Process of making dimensionally stable nonwoven fibrous webs

ABSTRACT

Dimensionally stable nonwoven fibrous webs include a multiplicity of continuous fibers formed from one or more thermoplastic polyesters and polypropylene in an amount greater than 0% and no more than 10% by weight of the web. The webs have at least one dimension which decreases by no greater than 10% in the plane of the web when heated to a temperature above a glass transition temperature of the fibers. A spunbond process may be used to produce substantially continuous fibers that exhibit molecular orientation. A meltblown process may be used to produce discontinuous fibers that do not exhibit molecular orientation. In some embodiments, the fibers comprise a viscosity modifier and/or an anionic surfactant. The webs may be used as articles for filtration, sound absorption, thermal insulation, surface cleaning, cellular growth support, drug delivery, personal hygiene, medical apparel, or wound dressing.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. patent application Ser. No.12/971,186, filed Dec. 17, 2010, issued as a U.S. Pat. No. 8,721,943 onMay 13, 2014, which claims the benefit of U.S. Provisional PatentApplication No. 61/287,697, filed Dec. 17, 2009, which are incorporatedherein by reference in their entirety.

BACKGROUND

Melt-spinning (or spunbonding) is the process of forming fibers byextruding molten polymer through small orifices in a die, collecting thespun filaments on a belt in a uniform random fashion, and bonding thefibers to form a cohesive web. Melt-blowing (or MB) is the process offorming fibers by extruding molten polymer through small orificessurrounded by high speed heated gas jets, and collecting the blownfilaments as a cohesive web. This process is also referred to as a blownmicro fiber (or BMF) process. The most common thermoplastic materialused for the BMF process is polypropylene, which produces a very finefiber with good thermal stability.

Polyesters such as poly(ethylene) terephthalate (PET) and polyolefinssuch as poly(propylene) (PP) are two commonly used classes of petroleumbased polymers in the commercial production of textile fibers, packagingfilms, beverage bottles, and injection molded goods by processes such asBMF and spunbond. Although PET has a higher melting point and superiormechanical and physical properties compared to other commercially usefulpolymers, it exhibits poor dimensional stability at temperatures aboveits glass transition temperature. Polyester fibers, e.g. aromaticpolyesters such as PET and poly(ethylene) terephthalate glycol (PETG),and/or aliphatic polyesters such as poly(lactic acid) (PLA), and websincluding such fibers, may shrink up to 40% of the original length whensubjected to elevated temperatures due to the relaxation of the orientedamorphous segments of the molecules to relax upon exposure to heat (SeeNarayanan, V.; Bhat, G. S. and L. C. Wadsworth. TAPPI Proceedings:Nonwovens Conference & Trade Fair. (1998) 29-36).

Furthermore, PET has generally not been considered as suitable forapplications involving high-speed processing because of its slowcrystallization from the melt state; at commercial production rates, thepolymer has minimal opportunity to form well developed crystallites.Articles prepared from PET fibers typically need to undergo anadditional stage of drawing and heat-setting (e.g. annealing) during thefiber spinning process to dimensionally stabilize the producedstructure.

Additionally, there is also a growing interest in replacingpetroleum-based polymers, such as PET and polypropylene (PP), withresource renewable polymers, i.e., polymers derived from plant basedmaterials. Ideal resource renewable polymers are “carbon dioxideneutral” meaning that as much carbon dioxide is consumed in growing theplants base material as is given off when the product is made anddisposed of. Biodegradable materials have adequate properties to permitthem to break down when exposed to conditions which lead to composting.Examples of materials thought to be biodegradable include aliphaticpolyesters such as poly(lactic acid) (PLA), poly(glycolic acid),poly(caprolactone), copolymers of lactide and glycolide, poly(ethylenesuccinate), and combinations thereof.

However, difficulty is often encountered in the use of aliphaticpolyesters such as poly(lactic acid) for BMF due to aliphatic polyesterthermoplastics having relatively high melt viscosities which yieldsnonwoven webs that generally cannot be made at the same fiber diametersthat polypropylene can on standard nonwoven production equipment such asspunbond and BMF production lines. The coarser fiber diameters ofpolyester webs can limit their application as many final productproperties are controlled by fiber diameter. For example, course fiberslead to a noticeably stiffer and less appealing feel for skin contactapplications. Furthermore, course fibers produce webs with largerporosity that can lead to webs that have less of a barrier property,e.g. less repellency to aqueous fluids.

The processing of aliphatic polyesters as microfibers has been describedin U.S. Pat. No. 6,645,618 (Hobbs et al.) and U.S. Pat. No. 6,645,618.U.S. Pat. No. 6,111,160 (Gruber et. al.) discloses the use of meltstable polylactides to form nonwoven articles via melt blown andspunbound processes. JP6466943A (Shigemitsu et al.) describes a lowshrinkage-characteristic polyester system and its manufacture approach.U.S. Patent Application Publication No. 2008/0160861 (Berrigan et al.)describes a method for making a bonded nonwoven fibrous web comprisingextruding melt blown fibers of a polyethylene terephthalate andpolylactic acid, collecting the melt blown fibers as an initial nonwovenfibrous web, and annealing the initial nonwoven fibrous web with acontrolled heating and cooling operation. U.S. Pat. No. 5,364,694 (Okadaet al.) describes a polyethylene terephthalate (PET) based meltblownnonwoven fabric and its manufacture. U.S. Pat. No. 5,753,736 (Bhat etal.) describes the manufacture of polyethylene terephthalate fiber withreduced shrinkage through the use of nucleation agent, reinforcer and acombination of both.

U.S. Pat. Nos. 5,585,056 and 6,005,019 describe a surgical articlecomprising absorbable polymer fibers and a plasticizer containingstearic acid and its salts.

Thermoplastic polymers are widely employed to create a variety ofproducts, including blown and cast films, extruded sheets, foams,fibers, monofilament and multifilament yarns, and products madetherefrom, woven and knitted fabrics, and non-woven fibrous webs.Traditionally, many of these articles have been made frompetroleum-based thermoplastics such as polyolefins.

Degradation of aliphatic polyesters can occur through multiplemechanisms including hydrolysis, transesterification, chain scission,and the like. Instability of such polymers during processing can occurat elevated temperatures as described in WO94/07941 (Gruber et al.).

Many thermoplastic polymers used in these products, such aspolyhydroxyalkanoates (PHA), are inherently hydrophobic. That is, as awoven, knit, or nonwoven such as a spunbond fabric, they will not absorbwater. There are a number of uses for thermoplastic polymers where theirhydrophobic nature either limits their use or requires some effort tomodify the surface of the shaped articles made therefrom. For example,polylactic acid has been reported to be used in the manufacture ofnonwoven webs that are employed in the construction of absorbentarticles such as diapers, feminine care products, and personalincontinence products (U.S. Pat. No. 5,910,368). These materials wererendered hydrophilic through the use of a post treatment topicalapplication of a silicone copolyol surfactant. Such surfactants are notthermally stable and can break down in an extruder to yieldformaldehyde.

U.S. Pat. No. 7,623,339 discloses a polyolefin resin renderedantimicrobial and hydrophilic using a combination of fatty acidmonoglycerides and enhancer(s).

Coating methods to provide a hydrophilic surface are known, but alsohave some limitations. First of all, the extra step required in coatingpreparation is expensive and time consuming. Many of the solvents usedfor coating are flammable liquids or have exposure limits that requirespecial production facilities. The quantity of surfactant can also belimited by the solubility of the surfactant in the coating solvent andthe thickness of the coating.

Post treatment of the thermoplastic polymer can be undesirable for atleast two other reasons. First, it can be more expensive since itrequires additional processing steps of surfactant application anddrying. Second, PHAs are polyesters, and thus prone to hydrolysis. It isdesirable to limit the exposure of PHA polymers to water which can bepresent in the surfactant application solution. Furthermore, thesubsequent drying step at elevated temperature in the wet web is highlyundesirable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the drop in pump exit back pressure with theaddition of an exemplary viscosity modifier.

FIG. 2 is an image of a Transmission Electron Microscopy of PLA fiberalone as a control.

FIG. 3 is an image of a Transmission Electron Microscopy of PLA fiberwith 5% by weight of polypropylene dispersed in the fiber.

FIG. 4 is a graph showing the normalized tensile load in the crossdirection for spunbond nonwoven webs made according to Example 26.

FIG. 5 is a graph showing the normalized tensile load in the machinedirection for spunbond nonwoven webs made according to Example 26.

SUMMARY

The present disclosure relates to dimensionally stable nonwoven fibrouswebs and methods of making and using such webs. The disclosure furtherrelates to dimensionally stable nonwoven fibrous webs including blendsof polypropylene and an aliphatic and/or aromatic polyester useful inmaking articles, such as biodegradable and biocompatible articles.

In one aspect, the disclosure relates to a web including a plurality ofcontinuous fibers comprising one or more thermoplastic polyestersselected from aliphatic polyesters and aromatic polyesters; andpolypropylene in an amount greater than 0% and no more than 10% byweight of the web, wherein the fibers exhibit molecular orientation andextend substantially endlessly through the web, and further wherein theweb has at least one dimension which decreases by no greater than 10% inthe plane of the web when the web is heated to a temperature above aglass transition temperature of the fibers, but below the melting pointof the fibers in an unrestrained condition. In some exemplaryembodiments, the molecular orientation of the fibers results in abi-refringence value of at least 0.01. In most embodiments, the fibersare microfibers, and particularly fine fibers.

In some exemplary embodiments, the thermoplastic polyester comprises atleast one aromatic polyester. In certain exemplary embodiments, thearomatic polyester is selected from poly(ethylene) terephthalate (PET),poly(ethylene) terephthalate glycol (PETG), poly(butylene) terephthalate(PBT), poly(trimethyl) terephthalate (PTT), their copolymers, orcombinations thereof. In other exemplary embodiments, the thermoplasticpolyester comprises at least one aliphatic polyester. In certainexemplary embodiments, the aliphatic polymer is selected from one ormore poly(lactic acid), poly(glycolic acid), poly(lactic-co-glycolicacid), polybutylene succinate, polyethylene adipate,polyhydroxy-butyrate, polyhydroxyvalerate, blends, and copolymersthereof. In certain exemplary embodiments, the aliphatic polyester issemicrystalline.

In another aspect, the disclosure relates to a web including a pluralityof fibers comprising one or more thermoplastic polyesters selected fromaliphatic polyesters; and polypropylene in an amount greater than 0% andno more than 10% by weight of the web, wherein the fibers do not exhibitmolecular orientation, and further wherein the web has at least onedimension which decreases by no greater than 10% in the plane of the webwhen the web is heated to a temperature above a glass transitiontemperature of the fibers, but below the melting point of the fibers. Incertain exemplary embodiments, the thermoplastic polyester comprises atleast one aliphatic polyester selected from the group consisting of oneor more poly(lactic acid), poly(glycolic acid), poly(lactic-co-glycolicacid), polybutylene succinate, polyethylene adipate,polyhydroxy-butyrate, polyhydroxyvalerate, blends, and copolymersthereof. In certain exemplary embodiments, the aliphatic polyester issemicrystalline. In most embodiments, the fibers are microfibers,particularly fine fibers.

In additional exemplary embodiments related to both of the previouslydescribed aspects of the disclosure, the plurality of fibers maycomprise a thermoplastic (co)polymer distinct from the thermoplasticpolyester. In further exemplary embodiments, the fibers may comprise atleast one of a plasticizer, a diluent, a surfactant, a viscositymodifier, an antimicrobial component, or combinations thereof. In someparticular exemplary embodiments, the fibers exhibit a median fiberdiameter of no greater than about 25 μm. In certain of theseembodiments, the fibers exhibit a median fiber diameter of no greaterthan 12 μm. In other embodiments, the fibers exhibit a median fiberdiameter of no greater than 8 μm. In certain of these embodiments, thefibers exhibit a median fiber diameter of at least 1 μm. In additionalexemplary embodiments, the web is biocompatible.

The present disclosure is also directed to fine fibers of aliphaticpolyesters, articles made with the fine fibers, and a method for makingthe aliphatic polyester fine fibers by a blown microfiber (BMF) process.The fibers may be melt-processable and have utility in a variety of foodsafety, medical, personal hygiene, disposable and reusable garments, andwater purification applications.

A melt blown web of the fine fibers is formed by use of a viscositymodifier to reduce the viscosity of the aliphatic polyesters, such asPLA. In certain exemplary embodiments, the viscosity modifier isselected from the group consisting of alkyl carboxylates and carboxylicacids, alkenyl carboxylates and carboxylic acids, aralkyl carboxylatesand carboxylic acids, alkylethoxylated carboxylates and carboxylicacids, aralkylethoxylated carboxylates and carboxylic acids, alkyllactylates and carboxylic acids, alkenyl lactylates and carboxylicacids, and mixtures thereof. By dramatically reducing the viscosity ofthe aliphatic polyester during the BMF process, the average diameter ofthe fibers is reduced, resulting in fine fibers, typically less than 12microns, in the melt blown web.

In some exemplary embodiments, the web is a dimensionally stablenonwoven fibrous web formed from a molten mixture of the thermoplasticpolyester and the polypropylene. In further exemplary embodiments, thedimensionally stable nonwoven fibrous web is selected from the groupconsisting of a spunbond web, a blown microfiber web, a hydroentangledweb, or combinations thereof.

In a further aspect, the disclosure relates to a method of making adimensionally stable nonwoven fibrous web comprising forming a mixtureof one or more thermoplastic polyesters selected from aliphaticpolyesters and aromatic polyesters with polypropylene in an amountgreater than 0% and no more than 10% by weight of the mixture; forming aplurality of fibers from the mixture; and collecting at least a portionof the fibers to form a web, wherein the fibers exhibit molecularorientation and extend substantially endlessly through the web, andfurther wherein the web has at least one dimension in the plane of theweb which decreases by no greater than 10% when the web is heated to atemperature above a glass transition temperature of the fibers, butbelow the melting point of the fibers when measured with the web in anunrestrained condition. In some embodiments, the fibers may be formedusing melt-spinning, filament extrusion, electrospinning, gas jetfibrillation or combinations thereof.

In still another aspect, the disclosure relates to a method of making adimensionally stable nonwoven fibrous web comprising forming a mixtureof one or more thermoplastic aliphatic polyesters with polypropylene inan amount greater than 0% and no more than 10% by weight of the mixture;forming a plurality of fibers from the mixture; and collecting at leasta portion of the fibers to form a web, wherein the fibers do not exhibitmolecular orientation, and further wherein the web has at least onedimension which decreases by no greater than 10% in the plane of the webwhen the web is heated to a temperature above a glass transitiontemperature of the fibers, but below the melting point of the fibers. Insome exemplary embodiments, the fibers may be formed using amelt-blowing (e.g. BMF) process.

In some exemplary embodiments, the methods may further comprise postheating the dimensionally stable nonwoven fibrous web, for example, bycontrolled heating or cooling of the web.

In a further aspect, the disclosure relates to an article comprising adimensionally stable nonwoven fibrous web as described above, whereinthe article is selected from a gas filtration article, a liquidfiltration article, a sound absorption article, a thermal insulationarticle, a surface cleaning article, a cellular growth support article,a drug delivery article, a personal hygiene article, a wound dressingarticle, an adhesive coated tape, and a dental hygiene article. Incertain exemplary embodiments, the article may be a surgical or medicaldrape. In other exemplary embodiments, the article may be a surgical ormedical gown. In other exemplary embodiments, the article may be asterilization wrap. In further exemplary embodiments, the article may bea wound contact material.

Exemplary aliphatic polyesters are poly(lactic acid), poly(glycolicacid), poly(lactic-co-glycolic acid), polybutylene succinate,polyhydroxybutyrate, polyhydroxyvalerate, blends, and copolymersthereof.

Articles made with the fine fibers comprise molded polymeric articles,polymeric sheets, polymeric fibers, woven webs, nonwoven webs, porousmembranes, polymeric foams, layered fine fibers, composite webs such asSMS (Spunbond, Meltblown, Spunbond), SMMS, and combinations thereof madeof the fine fibers described herein including thermal or adhesivelaminates. Examples of useful articles of this disclosure are woundcontact materials made of a film, foam and/or woven or nonwovencomprising the fine fibers and sterilization wraps, surgical drapes orsurgical gowns made at least in part of the fine fibers.

Products such as medical gowns, medical drapes, sterilization wraps,wipes, absorbents, insulation, and filters can be made from melt-blownfine fibers of aliphatic polyesters, such as PLA. Films, membranes,nonwovens, scrims and the like can be extrusion bonded or thermallylaminated directly to the webs.

Exemplary embodiments of the dimensionally stable nonwoven fibrous websaccording to the present disclosure may have structural features thatenable their use in a variety of applications, have exceptionalabsorbent properties, exhibit high porosity and permeability due totheir low solidity, and/or be manufactured in a cost-effective manner.Due to the small diameter of the fibers formed (fine fibers), the websmay have a soft feel similar to polyolefin webs but in many casesexhibit superior tensile strength due to the higher modulus of thealiphatic polyester used.

Bi-component fibers, such as core-sheath or side-by-side bi-componentfibers, may be prepared, as may be bicomponent microfibers, includingsub-micrometer fibers. However, exemplary embodiments of the disclosuremay be particularly useful and advantageous with monocomponent fibers.Among other benefits, the ability to use monocomponent fibers reducescomplexity of manufacturing and places fewer limitations on use of theweb.

Exemplary methods of producing dimensionally stable nonwoven fibrouswebs according to the present disclosure may have advantages in terms ofhigher production rate, higher production efficiency, lower productioncost, and the like.

Blends may be made using a variety of other polymers including aromaticpolyesters, aliphatic/aromatic copolyesters such as those described inU.S. Pat. No. 7,241,838 which is incorporated herein by reference,cellulose esters, cellulose ethers, thermoplastic starches, ethylenevinyl acetate, polyvinyl alcohol, ethylenevinyl alcohol, and the like.In blended compositions which include thermoplastic polymers which arenot aliphatic polyesters, the aliphatic polyester is typically presentat a concentration of greater than 70% by weight of total thermoplasticpolymer, preferably greater than 80% by weight of total thermoplasticpolymer and most preferably greater than about 90% by weight ofthermoplastic polymer. It was found that incorporation of other polymerscan significantly degrade the physical properties of the nonwovens made.This may be due to reduced crystallinity in the aliphatic polyester.Thus, for applications requiring strong nonwovens such as surgicaldrapes and gowns the amount of blended polymer or other additive otherthan the PP to reduce shrinkage, the surfactant to providehydrophilicity and the viscosity modifier to enable fine fiber formationshould be minimized. In these applications the amount of additives otherthan the PP and surfactant should be kept to less than 10% by weight ofthe aliphatic polyester, preferably less than 8% by weight of thealiphatic polyester, more preferably less than 5% by weight of thealiphatic polyester, and even more preferably less than 3% by weight ofthe polyester.

The present disclosure is also directed to a composition, article andmethod for making a durable hydrophilic and preferably biocompatiblecomposition. The composition and articles comprise the thermoplasticpolyesters and the surfactants as described herein. The method comprisesproviding the thermoplastic polyesters and the surfactants as describedherein, and mixing these materials sufficiently to yield abiocompatible, durable hydrophilic composition.

In another aspect, the polymer is solvent soluble or dispersible and thecomposition may be solvent cast, solvent spun to form films or fibers,or foams.

The melt processable composition of aliphatic polyesters and surfactantsexhibit durable hydrophilicity. In some cases the surfactant may bedissolved in or along with a surfactant carrier. The surfactant carrierand/or surfactant may be a plasticizer for the thermoplastic aliphaticpolyester.

The compositions of this invention are “relatively homogenous”. That is,the compositions can be produced by melt extrusion with good mixing andat the time of extrusion would be relatively homogenous in concentrationthroughout. It is recognized, however, that over time and/or with heattreatment the surfactant(s) may migrate to become higher or lower inconcentration at certain points, such as at the surface of the fiber.

In another aspect, a method of preparing durable hydrophilic fibers froma mixture or blend of thermoplastic film-forming aliphatic polyester,and at least one surfactant, is provided. The melt of the blend isprocessed or shaped, for example, by extrusion or molding to producefibers with the surfactants dissolved or dispersed within the fiber andpresent at the surfaces of the fiber to render those surfaces durablyhydrophilic. Because some surfactants demonstrate thermal sensitivity,the processing temperatures in the extruder are preferably kept belowabout 300° C., more preferably below about 250° C., and even morepreferably below 200° C. where those surfactants are exposed to suchtemperatures given the particular processing technique. The durablehydrophilicity is achieved without requiring post fiber finishingoperations, e.g. application of additional surfactant, because the fiberis durably hydrophilic as extruded, however, heating the web afterextrusion may help to bloom surfactant to the surface and improvehydrophilicity. This is done at temperatures at or above the glasstransition temperature of the thermoplastic(s) and is typically lessthan 120° C. and even less than 100° C.

The hydrophilicity imparted to the fiber compositions described hereinis done using at least one melt additive surfactant. Suitable anionicsurfactants include alkyl, alkenyl, alkaryl, or arakyl sulfate, alkyl,alkenyl, alkaryl, or arakyl sulfonate, alkyl, alkenyl alkaryl, or arakylphosphate, alkyl, alkenyl, alkaryl, or arakyl carboxylate or acombination thereof. The alkyl and alkenyl groups may be linear orbranched. These surfactants may be modified as is known in the art. Forexample, as used herein an “alkyl carboxylate” is a surfactant having analkyl group and a carboxylate group but it may also include, forexample, bridging moieties such as polyalkylene oxide groups, e.g.,isodeceth-7 carboxylate sodium salt is an alkyl carboxylate having abranched chain of ten carbons (C10) alkyl group, seven moles of ethyleneoxide and terminated in a carboxylate.

Various aspects and advantages of exemplary embodiments of the presentinvention have been summarized. The above Summary is not intended todescribe each illustrated embodiment or every implementation of thepresent invention. The Detailed Description and the Examples that followmore particularly exemplify certain presently preferred embodimentsusing the principles disclosed herein.

DETAILED DESCRIPTION

The present disclosure relates generally to dimensionally stablenonwoven fibrous webs or fabrics. The webs include a plurality of fibersformed from a (co)polymer mixture that is preferably melt processable,such that the (co)polymer mixture is capable of being extruded.Dimensionally stable nonwoven fibrous webs may be prepared by blendingan aliphatic and/or aromatic polyester with polypropylene (PP) in anamount greater than 0% and no more than 10% by weight of the web, beforeor during extrusion. The resulting webs have at least one dimensionwhich decreases by no greater than 10% in the plane of the web, when theweb is heated to a temperature above a glass transition temperature ofthe fibers while in an unrestrained condition. In certain embodiments,the fibers may exhibit molecular orientation.

In the plane of the web refers to the x-y plane of the web, which mayalso be referred to as the machine direction and/or cross direction ofthe web. Thus, fibers and webs described herein have at least onedimension in the plane of the web, e.g., the machine or the crossdirection, that decreases by no greater than 10%, when the web is heatedto a temperature above a glass transition temperature of the fibers.

The fibrous webs or fabrics as described herein are dimensionally stablewhen the web is heated to a temperature above a glass transitiontemperature of the fibers. The webs may be heated 15° C., 20° C., 30°C., 45° C. and even 55° C. above the glass transition temperature of thearomatic and/or aliphatic polyester fibers, and the web will remaindimensionally stable, e.g., having at least one dimension whichdecreases by no greater than 10% in the plane of the web. The web shouldnot be heated to a temperature that melts the fibers, or causes thefibers to appreciably degrade, as demonstrated by such characteristicsas loss of molecular weight or discoloration.

While not intending to be bound by theory, it is believed thataggregates of PP may thereby be evenly distributed through the core ofthe filament; the polyolefin is believed to act as a selectivelymiscible additive. At low weight percents of the web, PP mixes with thepolyester and physically inhibits chain movement, thereby suppressingcold crystallization, and macroscopic shrinkage is not observed. If theweight percent of the PP is increased further beyond 10 percent byweight, the PP and polyester phase separate and rearrangement of thepolyester is not affected.

In one preferred embodiment, the method of the present disclosurecomprises providing the aliphatic polyesters and the viscositymodifier(s) as described herein, and melt blowing these materialssufficiently to yield a web of fine fibers. While not intending to bebound by theory, the viscosity modifier likely does not plasticize themelt processable fine fibers of aliphatic polyesters. The compositionsare preferably non-irritating and non-sensitizing to mammalian skin andbiodegradable. The aliphatic polyester generally has a lower meltprocessing temperature and can yield a more flexible output material.

In another preferred embodiment the present invention discloses the useof melt additive anionic surfactants, optionally combined withsurfactant carriers such as polyethylene glycol, to impart stabledurable hydrophilicity to aliphatic polyester thermoplastics such aspolyhydroxyalkanoates (e.g. polylactic acid). Embodiments comprising theanionic surfactants described herein are particularly useful for makinghydrophilic absorbent polylactic acid nonwoven film laminate drapes usedin surgery, as well as personal care absorbents such as feminine hygienepads, diapers, incontinence pads, and the like. The use of these anionicsurfactants also provides useful antifog films when using transparentaliphatic polyesters. These antifog films may be used in food packaging,for safety eyewear and the like.

Hydrophilicity, or the lack thereof, can be measured in a variety ofways. For example, when water contacts a porous nonwoven web that ishydrophobic or has lost its hydrophilicity, the water does not flow, orflows undesirably slowly, through the web. Importantly the fibers andwebs of the present invention exhibit stable hydrophilicity (waterabsorbency). That is, they remain hydrophilic after aging in a clean butporous enclosure such as a poly/Tyvek pouch for over 30 days at 23° C.or lower and preferably for over 40 days.

Preferred materials of this invention wet with water and thus have anapparent surface energy of great than 72 dynes/cm (surface tension ofpure water). The most preferred materials of this invention instantlyabsorb water and remain water absorbent after aging for 10 days at 5°C., 23° C. and 45° C. More preferred materials of this inventioninstantly absorb water and remain water absorbent after aging for 20days at 5° C., 23° C. and 45° C. Even more materials of this inventioninstantly absorb water and remain water absorbent after aging for 30days at 5° C., 23° C. and 45° C.

Most preferred compositions remain hydrophilic (water absorbent) aftermore than 10 days at 45° C., preferably more than 30 days and mostpreferably greater than 40 days, when tested according to the methodsdescribed in the Examples. The preferred fabrics are instantaneouslywettable and absorbent and are capable of absorbing water at very highinitial rates.

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere in thespecification.

The term “biodegradable” means degradable by the action of naturallyoccurring microorganisms such as bacteria, fungi and algae and/ornatural environmental factors such as hydrolysis, transesterification,exposure to ultraviolet or visible light (photodegradable) and enzymaticmechanisms or combinations thereof.

The term “biocompatible” means biologically compatible by not producingtoxic, injurious or immunological response in living tissue.Biocompatible materials may also be broken down by biochemical and/orhydrolytic processes and absorbed by living tissue. Test methods usedinclude ASTM F719 for applications where the fine fibers contact tissuesuch as skin, wounds, mucosal tissue including in an orifice such as theesophagus or urethra, and ASTM F763 for applications where the finefibers are implanted in tissue.

The term “bi-component fiber” or “multi-component fiber” means fiberswith two or more components, each component occupying a part of thecross-sectional area of the fiber and extending over a substantiallength of the fiber. Suitable multi-component fiber configurationsinclude, but are not limited to, a sheath-core configuration, aside-by-side configuration, and an “islands-in-the-sea” configuration(for example, fibers produced by Kuraray Company, Ltd., Okayama, Japan).

The term “monocomponent fiber” means fibers in which the fibers haveessentially the same composition across their cross-section, butmonocomponent includes blends or additive-containing materials, in whicha continuous phase of substantially uniform composition extends acrossthe cross-section and over the length of the fiber. Fibers made ofblends in which the additive is heterogeneously dispersed in the polymerphase both across the cross section and along the fiber length isconsidered a monocomponent fiber.

The term “biodegradable” means degradable by the action of naturallyoccurring microorganisms such as bacteria, fungi and algae and/ornatural environmental factors such as hydrolysis, transesterification,exposure to ultraviolet or visible light (photodegradable) and enzymaticmechanisms or combinations thereof.

The term “biocompatible” means biologically compatible by not producingtoxic, injurious or immunological response in living tissue.Biocompatible materials may also be broken down by biochemical and/orhydrolytic processes and absorbed by living tissue. Test methods usedinclude ASTM F719 for applications where the fine fibers contact tissuesuch as skin, wounds, mucosal tissue including in an orifice such as theesophagus or urethra, and ASTM F763 for applications where the finefibers are implanted in tissue.

The term “durable hydrophilic” means that the composition, typically infiber or fabric form, remains water absorbent when aged at least 30 daysat 23° C. and preferably at least 40 days at 23° C.

The term “median fiber diameter” means fiber diameter determined byproducing one or more images of the fiber structure, such as by using ascanning electron microscope; measuring the fiber diameter of clearlyvisible fibers in the one or more images resulting in a total number offiber diameters, x; and calculating the median fiber diameter of the xfiber diameters. Typically, x is greater than about 20, more preferablygreater than about 50, and desirably ranges from about 50 to about 200.

The term “fine fiber” generally refers to fibers having a median fiberdiameter of no greater than about 50 micrometers (μm), preferably nogreater than 25 μm, more preferably no greater than 20 μm, still morepreferably no greater than 12 μm, even more preferably no greater than10 μm, and most preferably no greater than 5 μm.

“Microfibers” are a population of fibers having a median fiber diameterof at least one μm but no greater than 100 μm.

“Ultrafine microfibers” are a population of microfibers having a medianfiber diameter of two μm or less.

“Sub-micrometer fibers” are a population of fibers having a median fiberdiameter of no greater than one μm.

When reference is made herein to a batch, group, array, etc. of aparticular kind of microfiber, e.g., “an array of sub-micrometerfibers,” it means the complete population of microfibers in that array,or the complete population of a single batch of microfibers, and notonly that portion of the array or batch that is of sub-micrometerdimensions.

“Continuous oriented microfibers” herein refers to essentiallycontinuous fibers issuing from a die and traveling through a processingstation in which the fibers are drawn and at least portions of themolecules within the fibers are oriented into alignment with thelongitudinal axis of the fibers (“oriented” as used with respect tofibers means that at least portions of the molecules of the fibers arealigned along the longitudinal axis of the fibers).

“Melt-blown fibers” herein refers to fibers prepared by extruding moltenfiber-forming material through orifices in a die into a high-velocitygaseous stream, where the extruded material is first attenuated and thensolidifies as a mass of fibers.

“Separately prepared sub-micrometer fibers” means a stream ofsub-micrometer fibers produced from a sub-micrometer fiber-formingapparatus (e.g., a die) positioned such that the sub-micrometer fiberstream is initially spatially separate (e.g., over a distance of about 1inch (25 mm) or more from, but will merge in flight and disperse into, astream of larger size microfibers.

“Autogenous bonding” is defined as bonding between fibers at an elevatedtemperature as obtained in an oven or with a through-air bonder withoutapplication of direct contact pressure such as in point-bonding orcalendering.

“Molecularly same” polymer refers to polymers that have essentially thesame repeating molecular unit, but which may differ in molecular weight,method of manufacture, commercial form, etc.

“Self supporting” or “self sustaining” in describing a web means thatthe web can be held, handled and processed by itself, e.g., withoutsupport layers or other support aids.

“Solidity” is a nonwoven web property inversely related to density andcharacteristic of web permeability and porosity (low Soliditycorresponds to high permeability and high porosity), and is defined bythe equation:Solidity(%)=[3.937*Web Basis Weight(g/m2)]_[Web Thickness(mils)*BulkDensity(g/cm3)]

“Web Basis Weight” is calculated from the weight of a 10 cm×10 cm websample.

“Web Thickness” is measured on a 10 cm×10 cm web sample using athickness testing gauge having a tester foot with dimensions of 5cm×12.5 cm at an applied pressure of 150 Pa.

“Bulk Density” is the bulk density of the polymer or polymer blend thatmakes up the web, taken from the literature.

“Web” as used herein generally is a network of entangled fibers forminga sheet like or fabric like structure.

“Nonwoven” generally refers to fabric consisting of an assembly ofpolymeric fibers (oriented in one direction or in a random manner) heldtogether (1) by mechanical interlocking; (2) by fusing of thermoplasticfibers; (3) by bonding with a suitable binder such as a natural orsynthetic polymeric resin; or (4) any combination thereof.

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. Thus, for example, reference to fine fiberscontaining “a compound” includes a mixture of two or more compounds. Asused in this specification and the appended claims, the term “or” isgenerally employed in its sense including “and/or” unless the contentclearly dictates otherwise.

As used in this specification, the recitation of numerical ranges byendpoints includes all numbers subsumed within that range (e.g. 1 to 5includes 1, 1.5, 2, 2.75, 3, 3.8, 4, and 5).

Unless otherwise indicated, all numbers expressing quantities oringredients, measurement of properties and so forth used in thespecification and claims are to be understood as being modified in allinstances by the term “about.” Accordingly, unless indicated to thecontrary, the numerical parameters set forth in the foregoingspecification and attached claims are approximations that can varydepending upon the desired properties sought to be obtained by thoseskilled in the art utilizing the teachings of the present invention. Atthe very least, and not as an attempt to limit the application of thedoctrine of equivalents to the scope of the claims, each numericalparameter should at least be construed in light of the number ofreported significant digits and by applying ordinary roundingtechniques.

Various exemplary embodiments of the disclosure will now be described.Exemplary embodiments of the present invention may take on variousmodifications and alterations without departing from the spirit andscope of the disclosure. Accordingly, it is to be understood that theembodiments of the present invention are not to be limited to thefollowing described exemplary embodiments, but is to be controlled bythe limitations set forth in the claims and any equivalents thereof.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “one or more embodiments” or “an embodiment,” whether ornot including the term “exemplary” preceding the term “embodiment,”means that a particular feature, structure, material, or characteristicdescribed in connection with the embodiment is included in at least oneembodiment of the present invention. Thus, the appearances of thephrases such as “in one or more embodiments,” “in certain embodiments,”“in one embodiment” or “in an embodiment” in various places throughoutthis specification are not necessarily referring to the same embodimentof the present invention. Furthermore, the particular features,structures, materials, or characteristics may be combined in anysuitable manner in one or more embodiments.

A. Dimensionally Stable Nonwoven Fibrous Webs

In some embodiments, dimensionally stable nonwoven webs may be formedfrom a molten mixture of a thermoplastic polyester and a polypropylene.In certain embodiments, the dimensionally stable nonwoven webs may be aspunbond web, a blown microfiber web, a hydroentangled web, orcombinations thereof. These webs may be post processed into other forms.For example, they may be embossed, apertured, perforated, microcreped,laminated, etc. in order to provide additional properties. It isparticularly advantageous that post processing thermal processes can beaccomplished without shrinkage or loss of hydrophilicity on fine fiberfabrics.

1. Molecularly Oriented Fibers

In certain embodiments, dimensionally stable nonwoven fibrous webs canbe prepared by fiber-forming processes in which filaments offiber-forming material are formed by extrusion of a mixture of one ormore thermoplastic polyesters selected from aliphatic and aromaticpolyesters with polypropylene in an amount greater than 0% and no morethan 10% by weight of the mixture, subjected to orienting forces, andpassed through a turbulent field of gaseous currents while at least someof the extruded filaments are in a softened condition and reach theirfreezing temperature (e.g., the temperature at which the fiber-formingmaterial of the filaments solidifies) while in the turbulent field. Suchfiber formations processes include, for example, melt-spinning (i.e.spunbond), filament extrusion, electrospinning, gas jet fibrillation orcombinations thereof.

The resulting webs have at least one dimension which decreases by nogreater than 10% in the plane of the web when the web is heated to atemperature above a glass transition temperature of the fibers. Theglass transition temperature of the fibers may be determinedconventionally as is known in the art, for example, using differentialscanning calorimetry (DSC), or modulated DSC. In certain exemplaryembodiments, the thermoplastic polyester may be selected to include atleast one aromatic polyester. In other exemplary embodiments, thearomatic polyester may be selected from PET, PETG, poly(butylene)terephthalate (PBT), poly(trimethyl) terephthalate (PTT), orcombinations thereof.

As noted above, the fibers are preferably molecularly oriented; i.e.,the fibers preferably comprise molecules that are aligned lengthwise ofthe fibers and are locked into (i.e., are thermally trapped into) thatalignment. Oriented fibers are fibers where there is molecularorientation within the fiber. Fully oriented and partially orientedpolymeric fibers are known and commercially available. Orientation offibers can be measured in a number of ways, including birefringence,heat shrinkage, X-ray scattering, and elastic modulus (see e.g.Principles of Polymer Processing, Zehev Tadmor and Costas Gogos, JohnWiley and Sons, New York, 1979, pp. 77-84). It is important to note thatmolecular orientation is distinct from crystallinity, as bothcrystalline and amorphous materials can exhibit molecular orientationindependent from crystallization. Thus, even though commercially knownsub-micrometer fibers made by melt-blowing or electrospinning are notoriented, there are known methods of imparting molecular orientation tofibers made using those processes.

Oriented fibers prepared according exemplary embodiments of thedisclosure may show a difference in birefringence from segment tosegment. By viewing a single fiber through a polarized microscope andestimating retardation number using the Michel-Levy chart (see On-LineDetermination of Density and Crystallinity During Melt Spinning, VishalBansal et al, Polymer Engineering and Science, November 1996, Vol. 36,No. 2, pp. 2785-2798), birefringence is obtained with the followingformula: birefringence=retardation (nm)/1000D, where D is the fiberdiameter in micrometers. We have found that exemplary fibers susceptibleto birefringence measurements generally include segments that differ inbirefringence number by at least 5%, and preferably at least 10%. Someexemplary fibers may include segments that differ in birefringencenumber by 20 or even 50 percent. In some exemplary embodiments, themolecular orientation of the fibers results in a bi-refringence value ofat least 0.00001, more preferably at least about 0.0001, still morepreferably at least about 0.001, most preferably at least about 0.01.

Different oriented fibers or portions of an oriented fiber also mayexhibit differences in properties as measured by differential scanningcalorimetry (DSC). For example, DSC tests on exemplary webs preparedaccording to the disclosure may reveal the presence of chain-extendedcrystallization by the presence of a dual melting peak. Ahigher-temperature peak may be obtained for the melting point for achain-extended, or strain-induced, crystalline portion; and another,generally lower-temperature peak may occur at the melting point for anon-chain-extended, or less-ordered, crystalline portion. The term“peak” herein means that portion of a heating curve that is attributableto a single process, e.g., melting of a specific molecular portion of afiber such as a chain-extended portion. The peaks may be sufficientlyclose to one another that one peak has the appearance of a shoulder ofthe curve defining the other peak, but they are still regarded asseparate peaks, because they represent melting points of distinctmolecular fractions.

In certain exemplary embodiments, the passive longitudinal segments ofthe fibers may be oriented to a degree exhibited by typical spunbondfibrous webs. In crystalline or semi-crystalline polymers, such segmentspreferably exhibit strain-induced or chain-extended crystallization(i.e., molecular chains within the fiber have a crystalline orderaligned generally along the fiber axis). As a whole, the web can exhibitstrength properties like those obtained in spunbond webs, while beingstrongly bondable in ways that a typical spunbond web cannot be bonded.And autogenously bonded webs of the invention can have a loft anduniformity through the web that are not available with the point-bondingor calendering generally used with spunbond webs.

While not intending to be bound by theory, it is believed that molecularorientation is improved through the use of fiber attenuation as is knownin the art (See U. W. Gedde, Polymer Physics, 1st Ed. Chapman & Hall,London, 1995, 298.) An increase in percent crystallinity of theattenuated fibers may thus be observed. The crystallites stabilize thefilaments by acting as anchoring which inhibit chain motion, andrearrangement and crystallization of the rigid amorphous fraction; asthe percentage of crystallinity is increased the rigid amorphous andamorphous fraction is decreased. Semi-crystalline, linear polymersconsist of a crystalline and an amorphous phase with both phases beingconnected by tie molecules. The tie-molecule appears in both phases;strain builds at the coupled interface and it appears particularlyobvious in the amorphous phase as observed in the broadening of theglass transition to higher temperatures in semi-crystalline polymers. Incases of strong coupling, the affected molecular segments are produce aseparate intermediate phase of the amorphous phase called the rigidamorphous fraction. The intermediate phase, forming the extendedboundary between the crystalline and amorphous phases, is characterizedby lower local entropy than that of the fully amorphous phase.

At temperatures above the glass transition and below the meltingtemperature of the material, the rigid amorphous fraction rearranges andcrystallizes; it undergoes cold crystallization. The percentages ofcrystalline and rigid amorphous material present in the fibers determinethe macroscopic shrinkage value. The presence of crystallites may act tostabilize the filaments by acting as anchoring or tie points and inhibitchain motion.

Furthermore, it is presently believed that a total percent crystallinityof at least about 30% is required for PET to show dimensional stabilityat elevated temperatures; this level of crystallinity can generally onlybe obtained in a pure polyester system by thermally annealing the webafter the fiber forming process. Additionally, in conventional meltspinning, 0.08 g/denier stress is generally required to inducecrystallization in-line without any type of additive. In a typicalspunbonding operation at production rates of 1 g/die hole/minute,spinning speeds of 6000 meters per minute are generally needed toproduce the required thread-line tension. However, most spunbondingsystems provide only filament speeds from 3,000-5,000 meters per minute(m/min).

We have found that preferred aliphatic polyester fabrics such as thosemade from PLA have at least 20% crystallinity, preferably at least 30%crystallinity and most preferably at least 50% crystallinity in order tohave optimum dimensional stability at elevated temperatures andmechanical properties such as tensile strength.

Thus, exemplary embodiments of the present disclosure may beparticularly useful in forming dimensionally stable nonwoven fibrouswebs including molecularly oriented fibers using a high production ratespunbonding process. For example, dimensionally stable nonwoven fibrouswebs of the present disclosure may, in some embodiments, be preparedusing a spunbonding process at rates of at least 5,000 m/min, morepreferably at least 6,000 m/min.

2. Non-molecularly Oriented Fibers

In alternative embodiments, dimensionally stable nonwoven fibrous webscan be prepared by fiber-forming processes in which substantiallynon-molecularly oriented filaments of fiber-forming material are formedfrom a mixture of one or more thermoplastic polyesters selected fromaliphatic polyesters with polypropylene in an amount greater than 0% andno more than 10% by weight of the mixture, before or during extrusion.The resulting webs have at least one dimension which decreases by nogreater than 10% in the plane of the web when the web is heated to atemperature above a glass transition temperature of the fibers. In someexemplary embodiments, the fibers may be formed using a melt-blowing(e.g. BMF) process.

3. Fiber Sizes

In some exemplary embodiments of the above referenced fiber-formingprocesses used to produce dimensionally stable nonwoven fibrous webs, apreferred fiber component is a fine fiber. In certain more preferredembodiments, a fine fiber component is a sub-micrometer fiber componentcomprising fibers having a median fiber diameter of no greater than onemicrometer (μm). Thus, in certain exemplary embodiments, the fibersexhibit a median diameter of no greater than about one micrometer (μm).In some exemplary embodiments, the sub-micrometer fiber componentcomprises fibers have a median fiber diameter ranging from about 0.2 μmto about 0.9 μm. In other exemplary embodiments, the sub-micrometerfiber component comprises fibers have a median fiber diameter rangingfrom about 0.5 μm to about 0.7 μm.

The sub-micrometer fiber component may comprise monocomponent fiberscomprising the above-mentioned polymers or copolymers (i.e.(co)polymers. In this exemplary embodiment, the monocomponent fibers mayalso contain additives as described below. Alternatively, the fibersformed may be multi-component fibers.

In other exemplary embodiments, the nonwoven fibrous webs of the presentdisclosure may additionally or alternatively comprise one or more coarsefiber components such as microfiber component. In some exemplaryembodiments, the coarse fiber component may exhibit a median diameter ofno greater than about 50 μm, more preferably no greater than 25 μm, morepreferably no greater than 20 μm, even more preferably no greater than12 μm, still more preferably no greater than 10 μm, and most preferablyno greater than 5 μm. In other exemplary embodiments, a preferred coarsefiber component is a microfiber component comprising fibers having amedian fiber diameter of at least 1 μm, more preferably at least 5 μm,more preferably still at least 10 μm, even more preferably at least 20μm, and most preferably at least 25 μm. In certain exemplaryembodiments, the microfiber component comprises fibers having a medianfiber diameter ranging from about 1 μm to about 100 μm. In otherexemplary embodiments, the microfiber component comprises fibers have amedian fiber diameter ranging from about 5 μm to about 50 μm.

4. Layered Structures

In other exemplary embodiments, a multi-layer nonwoven fibrous web maybe formed by overlaying on a support layer a dimensionally stabledimensionally stable nonwoven fibrous web comprising an overlayer ofmicrofibers on an underlayer comprising a population of sub-micrometerfibers, such that at least a portion of the sub-micrometer fiberscontact the support layer at a major surface of the single-layernonwoven web. In such embodiments of a multi-layer nonwoven fibrous web,it will be understood that the term “overlayer” is intended to describean embodiment wherein at least one layer overlays another layer in amulti-layer composite web. However, it will be understood that byflipping any multi-layer nonwoven fibrous web 180 degrees about acenterline, what has been described as an overlayer may become anunderlayer, and the disclosure is intended to cover such modification tothe illustrated embodiments. Furthermore, reference to “a layer” isintended to mean at least one layer, and therefore each illustratedembodiment of a multi-layer nonwoven fibrous web may include one or moreadditional layers (not shown) within the scope of the disclosure. Inaddition, reference to “a layer” is intended to describe a layer atleast partially covering one or more additional layers (not shown).

For any of the previously described exemplary embodiments of adimensionally stable nonwoven fibrous web according to the presentdisclosure, the web will exhibit a basis weight, which may be varieddepending upon the particular end use of the web. Typically, thedimensionally stable nonwoven fibrous web has a basis weight of nogreater than about 1000 grams per square meter (gsm). In someembodiments, the nonwoven fibrous web has a basis weight of from about1.0 gsm to about 500 gsm. In other embodiments, the dimensionally stablenonwoven fibrous web has a basis weight of from about 10 gsm to about300 gsm. For use in some applications such as medical fabrics such assurgical drapes, surgical gowns and sterilization wraps the basis weightis from about 10 gsm to about 100 gsm and preferably 15 gsm to about 60gsm.

As with the basis weight, the nonwoven fibrous web will exhibit athickness, which may be varied depending upon the particular end use ofthe web. Typically, the dimensionally stable nonwoven fibrous web has athickness of no greater than about 300 millimeters (mm). In someembodiments, the dimensionally stable nonwoven fibrous web has athickness of from about 0.5 mm to about 150 mm. In other embodiments,the dimensionally stable nonwoven fibrous web has a thickness of fromabout 1.0 mm to about 50 mm. For use in some applications such asmedical fabrics such as surgical drapes, surgical gowns andsterilization wraps the thickness is from about 0.1 mm to about 10 mmand preferably 0.25 mm to about 2.5 mm.

5. Optional Support Layer

The dimensionally stable nonwoven fibrous webs of the present disclosuremay further comprise a support layer. When present, the support layermay provide most of the strength of the nonwoven fibrous article. Insome embodiments, the above-described sub-micrometer fiber componenttends to have very low strength, and can be damaged during normalhandling. Attachment of the sub-micrometer fiber component to a supportlayer lends strength to the sub-micrometer fiber component, whileretaining the low Solidity and hence the desired absorbent properties ofthe sub-micrometer fiber component. A multi-layer dimensionally stablenonwoven fibrous web structure may also provide sufficient strength forfurther processing, which may include, but is not limited to, windingthe web into roll form, removing the web from a roll, molding, pleating,folding, stapling, weaving, and the like.

A variety of support layers may be used in the present disclosure.Suitable support layers include, but are not limited to, a nonwovenfabric, a woven fabric, a knitted fabric, a foam layer, a film, a paperlayer, an adhesive-backed layer, a foil, a mesh, an elastic fabric(i.e., any of the above-described woven, knitted or nonwoven fabricshaving elastic properties), an apertured web, an adhesive-backed layer,or any combination thereof. In one exemplary embodiment, the supportlayer comprises a polymeric nonwoven fabric. Suitable nonwoven polymericfabrics include, but are not limited to, a spunbonded fabric, ameltblown fabric, a carded web of staple length fibers (i.e., fibershaving a fiber length of no greater than about 100 mm), a needle-punchedfabric, a split film web, a hydroentangled web, an airlaid staple fiberweb, or a combination thereof. In certain exemplary embodiments, thesupport layer comprises a web of bonded staple fibers. As describedfurther below, bonding may be effected using, for example, thermalbonding, ultrasonic bonding, adhesive bonding, powdered binder bonding,hydroentangling, needlepunching, calendering, or a combination thereof.

The support layer may have a basis weight and thickness depending uponthe particular end use of the nonwoven fibrous article. In someembodiments of the present disclosure, it is desirable for the overallbasis weight and/or thickness of the nonwoven fibrous article to be keptat a minimum level. In other embodiments, an overall minimum basisweight and/or thickness may be required for a given application.Typically, the support layer has a basis weight of no greater than about150 grams per square meter (gsm). In some embodiments, the support layerhas a basis weight of from about 5.0 gsm to about 100 gsm. In otherembodiments, the support layer has a basis weight of from about 10 gsmto about 75 gsm. In some embodiments where higher strength supportlayers are possible the support layer should have a basis weight of atleast 1 gsm, preferably at least 2 gsm, even more preferably at least 5gsm, and even more preferably at least 10 gsm. Preferably the supportlayer has a basis weight of less than 50 gsm, preferably less than 25gsm, even more preferably less than 20 gsm, and even more preferablyless than 15 gsm.

As with the basis weight, the support layer may have a thickness, whichvaries depending upon the particular end use of the nonwoven fibrousarticle. Typically, the support layer has a thickness of no greater thanabout 150 millimeters (mm). In some embodiments, the support layer has athickness of from about 1.0 mm to about 35 mm. In other embodiments, thesupport layer has a thickness of from about 2.0 mm to about 25 mm. Inother embodiments the support layer has a thickness of 0.1 mm to about10 mm preferably from about 0.25 mm to about 2.5 mm and even morepreferably from about 0.25 mm to about 1 mm.

In certain exemplary embodiments, the support layer may comprise amicrofiber component, for example, a plurality of microfibers. In suchembodiments, it may be preferred to deposit the above-describedsub-micrometer fiber population directly onto the microfiber supportlayer to form a multi-layer dimensionally stable nonwoven fibrous web.Optionally, the above-described microfiber population may be depositedwith or over the sub-micrometer fiber population on the microfibersupport layer. In certain exemplary embodiments, the plurality ofmicrofibers comprising the support layer is compositionally the same asthe population of microfibers forming the overlayer.

The sub-micrometer fiber component may be permanently or temporarilybonded to a given support layer. In some embodiments of the presentdisclosure, the sub-micrometer fiber component is permanently bonded tothe support layer (i.e., the sub-micrometer fiber component is attachedto the support layer with the intention of being permanently bondedthereto).

In some embodiments of the present disclosure, the above-describedsub-micrometer fiber component may be temporarily bonded to (i.e.,removable from) a support layer, such as a release liner. In suchembodiments, the sub-micrometer fiber component may be supported for adesired length of time on a temporary support layer, and optionallyfurther processed on a temporary support layer, and subsequentlypermanently bonded to a second support layer.

In one exemplary embodiment of the present disclosure, the support layercomprises a spunbonded fabric comprising polypropylene fibers. In afurther exemplary embodiment of the present disclosure, the supportlayer comprises a carded web of staple length fibers, wherein the staplelength fibers comprise: (i) low-melting point or binder fibers; and (ii)high-melting point or structural fibers. Typically, the binder fibershave a melting point of at least 10° C. greater than a melting point ofthe structural fibers, although the difference between the melting pointof the binder fibers and structural fibers may be greater than 10° C.Suitable binder fibers include, but are not limited to, any of theabove-mentioned polymeric fibers. Suitable structural fibers include,but are not limited to, any of the above-mentioned polymeric fibers, aswell as inorganic fibers such as ceramic fibers, glass fibers, and metalfibers; and organic fibers such as cellulosic fibers.

As described above, the support layer may comprise one or more layers incombination with one another. In one exemplary embodiment, the supportlayer comprises a first layer, such as a nonwoven fabric or a film, andan adhesive layer on the first layer opposite the sub-micrometer fibercomponent. In this embodiment, the adhesive layer may cover a portion ofor the entire outer surface of the first layer. The adhesive maycomprise any known adhesive including pressure-sensitive adhesives, heatactivatable adhesives, etc. When the adhesive layer comprises apressure-sensitive adhesive, the nonwoven fibrous article may furthercomprise a release liner to provide temporary protection of thepressure-sensitive adhesive. Preferred pressure sensitive adhesivesinclude acrylates, silicones, rubber based adhesives, polyisobutylenebased adhesives, block copolymer adhesives such as those based onKraton™ type polymers, polyalpha olefin adhesives and the like. Mostpreferred adhesives are acrylate and silicone based pressure sensitiveadhesives.

6. Optional Additional Layers

The dimensionally stable nonwoven fibrous webs of the present disclosuremay comprise additional layers in combination with the sub-micrometerfiber component, the support layer, or both. One or more additionallayers may be present over or under an outer surface of thesub-micrometer fiber component, under an outer surface of the supportlayer, or both.

Suitable additional layers include, but are not limited to, acolor-containing layer (e.g., a print layer); any of the above-describedsupport layers; one or more additional sub-micrometer fiber componentshaving a distinct median fiber diameter and/or physical composition; oneor more secondary fine sub-micrometer fiber layers for additionalinsulation performance (such as a melt-blown web or a fiberglassfabric); foams; layers of particles; foil layers; films; decorativefabric layers; membranes (i.e., films with controlled permeability, suchas dialysis membranes, reverse osmosis membranes, etc.); netting; mesh;wiring and tubing networks (i.e., layers of wires for conveyingelectricity or groups of tubes/pipes for conveying various fluids, suchas wiring networks for heating blankets, and tubing networks for coolantflow through cooling blankets); or a combination thereof

7. Optional Attachment Devices

In certain exemplary embodiments, the dimensionally stable nonwovenfibrous webs of the present disclosure may further comprise one or moreattachment devices to enable the nonwoven fibrous article to be attachedto a substrate. As discussed above, an adhesive may be used to attachthe nonwoven fibrous article. In addition to adhesives, other attachmentdevices may be used. Suitable attachment devices include, but are notlimited to, any mechanical fastener such as screws, snaps, nails, clips,staples, stitching, thread, hook and loop materials, etc.

The one or more attachment devices may be used to attach the nonwovenfibrous article to a variety of substrates. Exemplary substratesinclude, but are not limited to, a vehicle component; an interior of avehicle (i.e., the passenger compartment, the motor compartment, thetrunk, etc.); a wall of a building (i.e., interior wall surface orexterior wall surface); a ceiling of a building (i.e., interior ceilingsurface or exterior ceiling surface); a building material for forming awall or ceiling of a building (e.g., a ceiling tile, wood component,gypsum board, etc.); a room partition; a metal sheet; a glass substrate;a door; a window; a machinery component; an appliance component (i.e.,interior appliance surface or exterior appliance surface); a surface ofa pipe or hose; a computer or electronic component; a sound recording orreproduction device; a housing or case for an appliance, computer, etc.

The fine fibers are particularly useful for making absorbent orrepellent aliphatic polyester nonwoven gowns and film laminate drapesused in surgery sterilization wraps for sterilization of equipment, aswell as personal care absorbents such as feminine hygiene pads, diapers,incontinence pads, wipes, fluid filters, insulation and the like.

In one embodiment, this invention provides fine fibers comprising athermoplastic aliphatic polyester polymer, e.g., polylactic acid,polyhydroxybutyrate and the like, and one or more viscosity modifiersselected from the group of alkyl, alkenyl, aralkyl, or alkarylcarboxylates, or combinations thereof. The viscosity modifier is presentin the melt extruded fiber in an amount sufficient to modify the meltviscosity of the aliphatic polyester. Typically, the viscosity modifieris present at less than 10 weight %, preferably less than 8 weight %,more preferably less than 7%, more preferably less than 6 weight %, morepreferably less than 3 weight %, and most preferably less than 2% byweight based on the combined weight of the aliphatic polyester andviscosity modifier. Also the viscosity modifier is typically added at aconcentration of at least 0.25% by weight of the aliphatic polyester,preferably at least 0.5% by weight of the aliphatic polyester, and mostpreferably at least 1% by weight of the aliphatic polyester.

In another aspect, films, fabrics and webs constructed from the finefibers are provided. The invention also provides useful articles madefrom fabrics and webs of fine fibers including medical drapes,sterilization wraps, medical gowns, aprons, filter media, industrialwipes and personal care and home care products such as diapers, facialtissue, facial wipes, wet wipes, dry wipes, disposable absorbentarticles and garments such as disposable and reusable garments includinginfant diapers or training pants, adult incontinence products, femininehygiene products such as sanitary napkins, panty liners and the like.The fine fibers of this invention also may be useful for producingthermal insulation for garments such as coats, jackets, gloves, coldweather pants, boots, and the like as well as acoustical insulation.

In yet another aspect, this invention provides multi-layer, aqueousliquid-absorbent articles comprising an aqueous media impervious backingsheet. For example, importantly some surgical drapes are liquidimpervious to prevent liquid that is absorbed into the top sheet fromwicking through to the skin surface where it would be contaminated withbacteria present on the skin. In other embodiments the construction mayfurther comprise an aqueous media permeable topsheet, and an aqueousliquid-absorbent (i.e., hydrophilic) layer constructed of theabove-described web or fabric juxtaposed there between useful, forinstance, in constructing disposable diapers, wipes or towels, sanitarynapkins, and incontinence pads.

In yet another aspect, a single or multi-layer aqueous repellent articlesuch as a sterilization wrap, a surgical or medical gown or apron can beformed at least in part of a web of fine fibers described herein, andhave aqueous fluid repellent properties. For example, an SMS web may beformed having fine fibers in at least the M (melt blown, blowmicrofiber) layer but they may also comprise the S (spunbond layer) aswell. The M layer may have further incorporated a repellent additive atthe surface of the fibers, such as a fluorochemical, silicone,hydrocarbon wax or combinations thereof. The repellent additive may beincorporated into the melt as the web is made, coated onto the fibersprior to web formation, or coated onto the formed or semi-formed web. Inthis manner, the sterilization wrap is rendered water repellent or thegown is rendered fluid repellent to avoid absorption of blood or otherbody fluids that may contain pathogenic microorganisms.

The fine fiber fabrics (nonwovens, wovens, or knits) of this inventionmay be rendered more repellent by treatment with numerous compounds. Forexample, the fabrics may be post web forming surface treatments whichinclude paraffin waxes, fatty acids, bee's wax, silicones,fluorochemicals and combinations thereof. For example, the repellentfinishes may be applied as disclosed in U.S. Pat. Nos. 5,027,803;6,960,642; and 7,199,197, all of which are incorporated by referenceherein in its entirety. Repellent finishes may also be melt additivessuch as those described in U.S. Pat. No. 6,262,180, which isincorporated by reference herein in its entirety.

This invention also provides a method of preparing the fine fibers froma mixture or blend of thermoplastic film-forming aliphatic polyesterpolymer, and at least one viscosity modifier. The viscosity modifier canbe conveniently compounded with the resin in the hopper or elsewherealong the extruder as long as good mixing is achieved to render asubstantially uniform mixture. Alternatively, the viscosity modifier maybe added into the extruder directly (without precompounding), forexample, using a positive displacement pump or weight loss feeder.

B. Dimensionally Stable Nonwoven Fibrous Web Components

Various components of exemplary dimensionally stable nonwoven fibrouswebs according to the present disclosure will now be described. In someexemplary embodiments, the dimensionally stable nonwoven fibrous websmay include a plurality of continuous fibers comprising one or morethermoplastic polyesters selected from aliphatic polyesters and aromaticpolyesters; and polypropylene in an amount greater than 0% and no morethan 10% by weight of the web, wherein the fibers exhibit molecularorientation and extend substantially endlessly through the web, andfurther wherein the web has at least one dimension which decreases by nogreater than 10% in the plane of the web when the web is heated to atemperature above a glass transition temperature of the fibers. Suchdimensionally stable nonwoven fibrous webs may be produced, in certainexemplary embodiments, using a spunbond or melt spinning process.

In other exemplary embodiments, the dimensionally stable nonwovenfibrous webs may include a plurality of fibers comprising one or morethermoplastic polyesters selected from aliphatic polyesters; andpolypropylene in an amount greater than 0% and no more than 10% byweight of the web, wherein the fibers do not exhibit molecularorientation, and further wherein the web has at least one dimension inthe plane of the web which decreases by no greater than 10% in the planeof the web when the web is heated to a temperature above a glasstransition temperature of the fibers. Such dimensionally stable nonwovenfibrous webs may be produced, in certain exemplary embodiments, using ameltblown or BMF process.

1. Thermoplastic Polyesters

The fibrous webs of the present disclosure include at least onethermoplastic polyester. In some exemplary embodiments an aromaticpolyester is used as a major component in the fiber-forming mixture. Incertain exemplary embodiments, the aromatic polyester is selectedpoly(ethylene) terephthalate (PET), poly(ethylene) terephthalate glycol(PETG), poly(butylene) terephthalate (PBT), poly(trimethyl)terephthalate (PTT), their copolymers, and combinations thereof.

In other exemplary embodiments, an aliphatic polyester is used as amajor component in the fiber-forming mixture. Aliphatic polyestersuseful in practicing embodiments of the present invention include homo-and copolymers of poly(hydroxyalkanoates), and homo- and copolymers ofthose aliphatic polyesters derived from the reaction product of one ormore polyols with one or more polycarboxylic acids that is typicallyformed from the reaction product of one or more alkanediols with one ormore alkanedicarboxylic acids (or acyl derivatives). Polyesters mayfurther be derived from multifunctional polyols, e.g. glycerin,sorbitol, pentaerythritol, and combinations thereof, to form branched,star, and graft homo- and copolymers. Miscible and immiscible blends ofaliphatic polyesters with one or more additional semicrystalline oramorphous polymers may also be used.

Exemplary aliphatic polyesters are poly(lactic acid), poly(glycolicacid), poly(lactic-co-glycolic acid), polybutylene succinate,polyethylene adipate, polyhydroxybutyrate, polyhydroxyvalerate, blends,and copolymers thereof. One particularly useful class of aliphaticpolyesters are poly(hydroxyalkanoates), derived by condensation orring-opening polymerization of hydroxy acids, or derivatives thereof.Suitable poly(hydroxyalkanoates) may be represented by the formula:H(O—R—C(O)—)nOHwhere R is an alkylene moiety that may be linear or branched having 1 to20 carbon atoms, preferably 1 to 12 carbon atoms optionally substitutedby catenary (bonded to carbon atoms in a carbon chain) oxygen atoms; nis a number such that the ester is polymeric, and is preferably a numbersuch that the molecular weight of the aliphatic polyester is at least10,000, preferably at least 30,000, and most preferably at least 50,000daltons. Although higher molecular weight polymers generally yield filmswith better mechanical properties, for both melt processed and solventcast polymers excessive viscosity is typically undesirable. Themolecular weight of the aliphatic polyester is typically no greater than1,000,000, preferably no greater than 500,000, and most preferably nogreater than 300,000 daltons. R may further comprise one or morecatenary (i.e. in chain) ether oxygen atoms. Generally, the R group ofthe hydroxy acid is such that the pendant hydroxyl group is a primary orsecondary hydroxyl group.

Useful poly(hydroxyalkanoates) include, for example, homo- andcopolymers of poly(3-hydroxybutyrate), poly(4-hydroxybutyrate),poly(3-hydroxyvalerate), poly(lactic acid) (as known as polylactide),poly(3-hydroxypropanoate), poly(4-hydropentanoate),poly(3-hydroxypentanoate), poly(3-hydroxyhexanoate),poly(3-hydroxyheptanoate), poly(3-hydroxyoctanoate), polydioxanone,polycaprolactone, and polyglycolic acid (i.e., polyglycolide).Copolymers of two or more of the above hydroxy acids may also be used,for example, poly(3-hydroxybutyrate-co-3-hydroxyvalerate),poly(lactate-co-3-hydroxypropanoate), poly(glycolide-co-p-dioxanone),and poly(lactic acid-co-glycolic acid). Blends of two or more of thepoly(hydroxyalkanoates) may also be used, as well as blends with one ormore polymers and/or copolymers.

Aliphatic polyesters useful in the inventive fine fibers may includehomopolymers, random copolymers, block copolymers, star-branched randomcopolymers, star-branched block copolymers, dendritic copolymers,hyperbranched copolymers, graft copolymers, and combinations thereof.

Another useful class of aliphatic polyesters includes those aliphaticpolyesters derived from the reaction product of one or more alkanediolswith one or more alkanedicarboxylic acids (or acyl derivatives). Suchpolyesters have the general formula:

where R′ and R″ each represent an alkylene moiety that may be linear orbranched having from 1 to 20 carbon atoms, preferably 1 to 12 carbonatoms, and m is a number such that the ester is polymeric, and ispreferably a number such that the molecular weight of the aliphaticpolyester is at least 10,000, preferably at least 30,000, and mostpreferably at least 50,000 daltons, but no greater than 1,000,000,preferably no greater than 500,000 and most preferably no greater than300,000 daltons. Each n is independently 0 or 1. R′ and R″ may furthercomprise one or more caternary (i.e. in chain) ether oxygen atoms.

Examples of aliphatic polyesters include those homo- and copolymersderived from (a) one or more of the following diacids (or derivativethereof): succinic acid; adipic acid; 1,12 dicarboxydodecane; fumaricacid; glutartic acid; diglycolic acid; and maleic acid; and (b) one ofmore of the following diols: ethylene glycol; polyethylene glycol;1,2-propane diol; 1,3-propanediol; 1,2-propanediol; 1,2-butanediol;1,3-butanediol; 1,4-butanediol; 2,3-butanediol; 1,6-hexanediol; 1,2alkane diols having 5 to 12 carbon atoms; diethylene glycol;polyethylene glycols having a molecular weight of 300 to 10,000 daltons,preferably 400 to 8,000 daltons; propylene glycols having a molecularweight of 300 to 4000 daltons; block or random copolymers derived fromethylene oxide, propylene oxide, or butylene oxide; dipropylene glycol;and polypropylene glycol, and (c) optionally a small amount, i.e.,0.5-7.0-mole % of a polyol with a functionality greater than two such asglycerol, neopentyl glycol, and pentaerythritol.

Such polymers may include polybutylenesuccinate homopolymer,polybutylene adipate homopolymer, polybutyleneadipate-succinatecopolymer, polyethylenesuccinate-adipate copolymer, polyethylene glycolsuccinate homopolymer and polyethylene adipate homopolymer.

Commercially available aliphatic polyesters include poly(lactide),poly(glycolide), poly(lactide-co-glycolide),poly(L-lactide-co-trimethylene carbonate), poly(dioxanone),poly(butylene succinate), and poly(butylene adipate).

Preferred aliphatic polyesters include those derived fromsemicrystalline polylactic acid. Poly(lactic acid) or polylactide haslactic acid as its principle degradation product, which is commonlyfound in nature, is non-toxic and is widely used in the food,pharmaceutical and medical industries. The polymer may be prepared byring-opening polymerization of the lactic acid dimer, lactide. Lacticacid is optically active and the dimer appears in four different forms:L,L-lactide, D,D-lactide, D,L-lactide (meso lactide) and a racemicmixture of L,L- and D,D-. By polymerizing these lactides as purecompounds or as blends, poly(lactide) polymers may be obtained havingdifferent stereochemistries and different physical properties, includingcrystallinity. The L,L- or D,D-lactide yields semicrystallinepoly(lactide), while the poly(lactide) derived from the D,L-lactide isamorphous.

The polylactide preferably has a high enantiomeric ratio to maximize theintrinsic crystallinity of the polymer. The degree of crystallinity of apoly(lactic acid) is based on the regularity of the polymer backbone andthe ability to crystallize with other polymer chains. If relativelysmall amounts of one enantiomer (such as D-) is copolymerized with theopposite enantiomer (such as L-) the polymer chain becomes irregularlyshaped, and becomes less crystalline. For these reasons, whencrystallinity is favored, it is desirable to have a poly(lactic acid)that is at least 85% of one isomer, more preferably at least 90% of oneisomer, or even more preferably at least 95% of one isomer in order tomaximize the crystallinity.

An approximately equimolar blend of D-polylactide and L-polylactide isalso useful. This blend forms a unique crystal structure having a highermelting point (˜210° C.) than does either the D-poly(lactide) andL-(polylactide) alone (˜160° C.), and has improved thermal stability,see. See H. Tsuji et al., Polymer, 40 (1999) 6699-6708.

Copolymers, including block and random copolymers, of poly(lactic acid)with other aliphatic polyesters may also be used. Useful co-monomersinclude glycolide, beta-propiolactone, tetramethylglycolide,beta-butyrolactone, gamma-butyrolactone, pivalolactone, 2-hydroxybutyricacid, alpha-hydroxyisobutyric acid, alpha-hydroxyvaleric acid,alpha-hydroxyisovaleric acid, alpha-hydroxycaproic acid,alpha-hydroxyethylbutyric acid, alpha-hydroxyisocaproic acid,alpha-hydroxy-beta-methylvaleric acid, alpha-hydroxyoctanoic acid,alpha-hydroxydecanoic acid, alpha-hydroxymyristic acid, andalpha-hydroxystearic acid.

Blends of poly(lactic acid) and one or more other aliphatic polyesters,or one or more other polymers may also be used. Examples of usefulblends include poly(lactic acid) and poly(vinyl alcohol), polyethyleneglycol/polysuccinate, polyethylene oxide, polycaprolactone andpolyglycolide.

Poly(lactide)s may be prepared as described in U.S. Pat. No. 6,111,060(Gruber, et al.), U.S. Pat. No. 5,997,568 (Liu), U.S. Pat. No. 4,744,365(Kaplan et al.), U.S. Pat. No. 5,475,063 (Kaplan et al.), U.S. Pat. No.6,143,863 (Gruber et al.), U.S. Pat. No. 6,093,792 (Gross et al.), U.S.Pat. No. 6,075,118 (Wang et al.), and U.S. Pat. No. 5,952,433 (Wang etal.), WO 98/24951 (Tsai et al.), WO 00/12606 (Tsai et al.), WO 84/04311(Lin), U.S. Pat. No. 6,117,928 (Hiltunen et al.), U.S. Pat. No.5,883,199 (McCarthy et al.), WO 99/50345 (Kolstad et al.), WO 99/06456(Wang et al.), WO 94/07949 (Gruber et al.), WO 96/22330 (Randall etal.), and WO 98/50611 (Ryan et al.), the disclosure of each patentincorporated herein by reference. Reference may also be made to J. W.Leenslag, et al., J. Appl. Polymer Science, vol. 29 (1984), pp2829-2842, and H. R. Kricheldorf, Chemosphere, vol. 43, (2001) 49-54.

The molecular weight of the polymer should be chosen so that the polymermay be processed as a melt. For polylactide, for example, the molecularweight may be from about 10,000 to 1,000,000 daltons, and is preferablyfrom about 30,000 to 300,000 daltons. By “melt-processible”, it is meantthat the aliphatic polyesters are fluid or can be pumped or extruded atthe temperatures used to process the articles (e.g. make the fine fibersin BMF), and do not degrade or gel at those temperatures to the extentthat the physical properties are so poor as to be unusable for theintended application. Thus, many of the materials can be made intononwovens using melt processes such as spun bond, blown microfiber, andthe like. Certain embodiments also may be injection molded. Thealiphatic polyester may be blended with other polymers but typicallycomprises at least 50 weight percent, preferably at least 60 weightpercent, and most preferably at least 65 weight percent of the finefibers.

2. Polypropylenes

Polypropylene (homo)polymers and copolymers useful in practicingembodiments of the present disclosure may be selected from polypropylenehomopolymers, polypropylene copolymers, and blends thereof (collectivelypolypropylene (co)polymers). The homopolymers may be atacticpolypropylene, isotactic polypropylene, syndiotactic polypropylene andblends thereof. The copolymer can be a random copolymer, a statisticalcopolymer, a block copolymer, and blends thereof. In particular, theinventive polymer blends described herein include impact (co)polymers,elastomers and plastomers, any of which may be physical blends or insitu blends with the polypropylene.

The method of making the polypropylene (co)polymer is not critical, asit can be made by slurry, solution, gas phase or other suitableprocesses, and by using catalyst systems appropriate for thepolymerization of polyolefins, such as Ziegler-Natta-type catalysts,metallocene-type catalysts, other appropriate catalyst systems orcombinations thereof. In a preferred embodiment the propylene(co)polymers are made by the catalysts, activators and processesdescribed in U.S. Pat. Nos. 6,342,566; 6,384,142; WO 03/040201; WO97/19991 and U.S. Pat. No. 5,741,563. Likewise, (co)polymers may beprepared by the process described in U.S. Pat. Nos. 6,342,566 and6,384,142. Such catalysts are well known in the art, and are describedin, for example, ZIEGLER CATALYSTS (Gerhard Fink, Rolf Mulhaupt and HansH. Brintzinger, eds., Springer-Verlag 1995); Resconi et al., Selectivityin Propene Polymerization with Metallocene Catalysts, 100 CHEM. REV.1253-1345 (2000); and I, II METALLOCENE-BASED POLYOLEFINS (Wiley & Sons2000).

Propylene (co)polymers that are useful in practicing some embodiments ofthe presently disclosed invention include those sold under thetradenames ACHIEVE and ESCORENE by Exxon-Mobil Chemical Company(Houston, Tex.), and various propylene (co)polymers sold by TotalPetrochemicals (Hoston, Tex.).

Presently preferred propylene homopolymers and copolymers useful in thisinvention typically have: 1) a weight average molecular weight (Mw) ofat least 30,000 Da, preferably at least 50,000 Da, more preferably atleast 90,000 Da, as measured by gel permeation chromatography (GPC),and/or no more than 2,000,000 Da, preferably no more than 1,000,000 Da,more preferably no more than 500,000 Da, as measured by gel permeationchromatography (GPC); and/or 2) a polydispersity (defined as Mw/Mn,wherein Mn is the number average molecular weight determined by GPC) of1, preferably 1.6, and more preferably 1.8, and/or no more than 40,preferably no more than 20, more preferably no more than 10, and evenmore preferably no more than 3; and/or 3) a melting temperature Tm(second melt) of at least 30° C., preferably at least 50° C., and morepreferably at least 60° C. as measured by using differential scanningcalorimetry (DSC), and/or no more than 200° C., preferably no more than185° C., more preferably no more than 175° C., and even more preferablyno more than 170° C. as measured by using differential scanningcalorimetry (DSC); and/or 4) a crystallinity of at least 5%, preferablyat least 10%, more preferably at least 20% as measured using DSC, and/orno more than 80%, preferably no more than 70%, more preferably no morethan 60% as measured using DSC; and/or 5) a glass transition temperature(Tg) of at least −40° C., preferably at least −10° C., more preferablyat least −10° C., as measured by dynamic mechanical thermal analysis(DMTA), and/or no more than 20° C., preferably no more than 10° C., morepreferably no more than 50° C., as measured by dynamic mechanicalthermal analysis (DMTA); and/or 6) a heat of fusion (Hf) of 180 J/g orless, preferably 150 J/g or less, more preferably 120 J/g or less asmeasured by DSC and/or at least 20 J/g, more preferably at least 40 J/gas measured by DSC; and/or 7) a crystallization temperature (Tc) of atleast 15° C., preferably at least 20° C., more preferably at least 25°C., even more preferably at least 60° C. and/or, no more than 120° C.,preferably no more than 115° C., more preferably no more than 110° C.,even more preferably no more than 145° C.

Exemplary webs of the present disclosure may include propylene(co)polymers (including both poly(propylene) homopolymers andcopolymers) in an amount of at least 1% by weight of the web, morepreferably at least about 2% by weight of the web, most preferably atleast 3% by weight of the web. Other exemplary webs may includepropylene (co)polymers (including both poly(propylene) homopolymers andcopolymers) in an amount no more than 10% by weight of the web, morepreferably in an amount no more than 8% by weight of the web, mostpreferably in an amount no more than 6% by weight of the web. In certainpresently preferred embodiments, the webs comprise polypropylene fromabout 1% to about 6% by weight of the web, more preferably from about 3%to no more than 5% by weight of the web.

3. Optional Additives

Fibers also may be formed from blends of materials, including materialsinto which certain additives have been blended, such as pigments ordyes. In addition to the fiber-forming materials mentioned above,various additives may be added to the fiber melt and extruded toincorporate the additive into the fiber. Typically, the amount ofadditives other than the PP and viscosity modifier is no greater thanabout 25 wt % of the polyester, desirably, no greater than about 10% byweight of the polyester, more desirably no greater than 5.0%, by weightof the polyester. Suitable additives include, but are not limited to,particulates, fillers, stabilizers, plasticizers, tackifiers, flowcontrol agents, cure rate retarders, adhesion promoters (for example,silanes and titanates), adjuvants, impact modifiers, expandablemicrospheres, thermally conductive particles, electrically conductiveparticles, silica, glass, clay, talc, pigments, colorants, glass beadsor bubbles, antioxidants, optical brighteners, antimicrobial agents,surfactants, wetting agents, fire retardants, and repellents such ashydrocarbon waxes, silicones, and fluorochemicals.

One or more of the above-described additives may be used to reduce theweight and/or cost of the resulting fiber and layer, adjust viscosity,or modify the thermal properties of the fiber or confer a range ofphysical properties derived from the physical property activity of theadditive including electrical, optical, density-related, liquid barrieror adhesive tack related properties.

Fillers (i.e. insoluble organic or inorganic materials generally addedto augment weight, size or to fill space in the resin for example todecrease cost or impart other properties such as density, color, imparttexture, effect degradation rate and the like) can detrimentally effectfiber properties. Fillers can be particulate nonthermoplastic orthermoplastic materials. Fillers also may be non-aliphatic polyesterspolymers which often are chosen due to low cost such as starch, lignin,and cellulose based polymers, natural rubber, and the like. These fillerpolymers tend to have little or no cyrstallinity.

Fillers, plasticizers, and other additives when used at levels above 3%by weight and certainly above 5% by weight of the aliphatic polyesterresin can have a significant negative effect on physical properties suchas tensile strength of the nonwoven web. Above 10% by weight of thealiphatic polyester these additives can have a dramatic negative effecton physical properties. Therefore, total additives other than thepolypropylene preferably are present at no more than 10% by weight,preferably no more than 5% by weight and most preferably no more than 3%by weight based on the weight of the polyester in the final nonwovenarticle. The compounds may be present at much higher concentrations inmasterbatch concentrates used to make the nonwoven. For example,nonwoven spunbond webs of the present invention having a basis weight of45 g/meter² preferably have a tensile strength of at least 30 N/mmwidth, preferably at least 40N/mm width. More preferably at least 50N/mm width and most preferably at least 60 N/mm width when tested onmechanical test equipment as specified in the Examples.

i) Plasticizers

In some exemplary embodiments, a plasticizer for the thermoplasticpolyester may be used in forming the fine fibers. In some exemplaryembodiments, the plasticizer for the thermoplastic polyester is selectedfrom poly(ethylene glycol), oligomeric polyesters, fatty acid monoestersand di-esters, citrate esters, or combinations thereof. Suitableplasticizers that may be used with the aliphatic polyesters include, forexample, glycols such glycerin; propylene glycol, polyethoxylatedphenols, mono or polysubstituted polyethylene glycols, higher alkylsubstituted N-alkyl pyrrolidones, sulfonamides, triglycerides, citrateesters, esters of tartaric acid, benzoate esters, polyethylene glycolsand ethylene oxide propylene oxide random and block copolymers having amolecular weight no greater than 10,000 Daltons (Da), preferably nogreater than about 5,000 Da, more preferably no greater than about 2,500Da; and combinations thereof.

ii) Diluent

In some exemplary embodiments, a diluent may be added to the mixtureused to form the fine fibers. In certain exemplary embodiments, thediluent may be selected from a fatty acid monoester (FAME), a PLAoligomer, or combinations thereof. Diluent as used herein generallyrefers to a material that inhibits, delays, or otherwise affectscrystallinity as compared to the crystallinity that would occur in theabsence of the diluent. Diluents may also function as plasticizers.

iii) Viscosity Modifiers

In some exemplary embodiments, fine fibers comprising a thermoplasticaliphatic polyester polymer, e.g., polylactic acid, polyhydroxybutyrateand the like, greater than 0% but 10% or less by weight ofpolypropylene, and one or more viscosity modifiers selected from thegroup of alkyl, alkenyl, aralkyl, or alkaryl carboxylates, orcombinations thereof, are formed using a fiber forming process.

The fine fibers disclosed herein may include one or more viscositymodifier(s) to reduce the average diameter of the fiber during the meltprocess (e.g. blown microfiber (BMF), spunbond, or injection molding).By reducing the viscosity of the aliphatic polyester during the BMFprocess, the average diameter of the fibers may be reduced, resulting infine fibers, typically no greater than 20 micrometers, in the melt blownweb. We have found that the addition of most known plasticizers for thealiphatic polyester thermoplastics result in a very gradual viscosityreduction. This is generally not useful for producing fine fibers ofsufficient mechanical strength since the plasticizers degrade polymerstrength. Viscosity reduction can be detected in the extrusion/BMFequipment by recording the pressures within the equipment.

The viscosity modifiers of the present invention result in a dramaticviscosity reduction, and thus reduce back pressure during extrusion orthermal processing. In many cases, the viscosity reduction is so greatthat the melt processing temperature must be reduced in order tomaintain sufficient melt strength. Often the melt temperature is reducedby 30° C. or more.

In applications in which biodegradability is important, it may bedesirable to incorporate biodegradable viscosity modifiers, whichtypically include ester and/or amide groups that may be hydrolyticallyor enzymatically cleaved. Exemplary viscosity modifiers useful in thefine fibers described herein include viscosity modifiers with thefollowing structure:(R—CO2⁻)_(n)M^(n+)where R is alkyl or alkylene of C8-C30, which is branched or straightchain, or C12-C30 aralkyl, and may be optionally substituted with 0-100alkylene oxide groups such as ethylene oxide, propylene oxide groups,oligameric lactic and/or glycolic acid or a combination thereof; and

M is H, an alkali metal or an alkaline earth metal salt, preferably Na+,K+, or Ca++, or amine salts including tertiary and quaternary aminessuch as protonated triethanolamine, tetramethylammonium and the like;

n is 1 or 2 and is the valence of the M group.

In the formula above, the ethylene oxide groups and propylene oxidegroups can occur in reverse order as well as in a random, sequential, orblock arrangement.

In certain preferred embodiments, the viscosity modifiers useful to formfine fibers are selected from the group consisting of alkylcarboxylates, alkenyl carboxylates, aralkyl carboxylates,alkylethoxylated carboxylates, aralkylethoxylated carboxylates, alkyllactylates, alkenyl lactylates, and mixtures thereof. The carboxylicacid equivalents of the carboxylates may also function as viscositymodifiers. Combinations of various viscosity modifiers can also be used.As used herein a lactylate is a surfactant having a hydrophobe and ahydrophile wherein the hydrophile is at least in part an oligamer oflactic acid having 1-5 lactic acid units, and typically having 1-3lactic acid units. A preferred lactylate is calcium stearoyl lactylatefrom Rita Corp. which is reported to have the following structure:[CH₃(CH₂)₁₆C(O)O—CH(CH₃)—C(O)O—CH(CH₃)—C(O)O—]₂Ca⁺⁺. Alkyl lactylatesare a preferred class of viscosity modifiers since these also are madefrom resource renewable materials.

The viscosity modifiers typically melt at or below the extrusiontemperature of the thermoplastic aliphatic polyester composition. Thisgreatly facilitates dispersing or dissolving the viscosity modifier inthe polymer composition. Mixtures of viscosity modifiers may be employedto modify the melting point. For example, mixtures of alkyl carboxylatesmay be preformed or an alkyl carboxylate may be blended with a nonionicsurfactant such as a polyethoxylated surfactant. The necessaryprocessing temperature may be altered by addition of nonsurfactantcomponents as well such as plasticizers for the thermoplastics aliphaticpolyester. For example, when added to polylactic acid compositions, theviscosity modifiers preferably have a melting point of no greater than200° C., preferably no greater than 180° C., more preferably no greaterthan 170° C., and even more preferably no greater than 160° C.

The viscosity modifier can be conveniently compounded with the resin inthe hopper or elsewhere along the extruder as long as good mixing isachieved to render a substantially uniform mixture. Alternatively, theviscosity modifier may be added into the extruder directly (withoutpre-compounding), for example, using a positive displacement pump orweight loss feeder.

The viscosity modifier may be present in the melt extruded fiber in anamount sufficient to modify the melt viscosity of aliphatic polyester.In most embodiments, the viscosity modifier is present at no greaterthan 10 weight %, preferably no greater than 8 weight %, more preferablyno greater than 7%, more preferably no greater than 6 weight %, morepreferably no greater than 3 weight %, and most preferably no greaterthan 2% by weight based on the combined weight of the aliphaticpolyester and viscosity modifier.

In some embodiments, when used in the fine fibers, the viscositymodifiers are present in a total amount of at least 0.25 wt.-%, at least0.5 wt.-%, at least 1.0 wt.-%, or at least 2.0 wt.-%, based on the totalweight of the fine fibers. In certain embodiments, in which a very lowviscosity melt is desired and/or a low melt temperature is preferred,the fine fibers comprise greater than 2 wt. %, greater than 3 wt. %, oreven greater than 5 wt. % of the viscosity modifier based on the weightof the aliphatic polyester polymer in the fine fibers.

For melt processing, preferred viscosity modifiers have low volatilityand do not decompose appreciably under process conditions. The preferredviscosity modifiers contain no greater than 10 wt. % water, preferablyno greater than 5% water, and more preferably no greater than 2 wt. %and even more preferably no greater than 1% water (determined by KarlFischer analysis). Moisture content is kept low in order to preventhydrolysis of the aliphatic polyester or other hydrolytically sensitivecompounds in the fine fibers.

Even though some of the viscosity modifiers are waxes at roomtemperature and often used as mold release agents, lubricants, and thelike surprisingly we have found that the nonwoven fabrics of thisinvention are able to be thermally bonded to themselves as well as otherfabrics. For example, the nonwoven fabrics of this invention have beensuccessfully heat seal bonded to a second fabric of this invention aswell as to polyolefin films, polyacrylate films, polyester nonwovens andthe like. It is believed that these fabrics may be bonded to a fabric,film, or foam using thermal heat, ultrasonic welding, and the like.Typically some pressure is applied to facilitate bonding. In the processtypically at least a portion of the fibers of the nonwoven fabric ofthis invention melt to form the bond. Bond patterns may be continuous(e.g. a continuous 5-10 mm wide seal) or patterned (e.g. a 5-10 mm widepattern of dots or any other geometric shape of bond patterns).

The viscosity modifiers may be carried in a nonvolatile carrier.Importantly, the carrier is typically thermally stable and can resistchemical breakdown at processing temperatures which may be as high as150° C., 200° C., 250° C., or even as high as 300° C. Preferred carriersfor hydrophilic articles include polyalkylene oxides such aspolyethylene glycol, polypropylene glycol, random and block copolymersof ethylene oxide and propylene oxide, thermally stable polyhydricalcohols such as propylene glycol, glycerin, polyglycerin, and the like.The polyalkylene oxides/polyalkylene glycols may be linear or brancheddepending on the initiating polyol. For example, a polyethylene glycolinitiated using ethylene glycol would be linear but one initiated withglycerin, trimethylolpropane, or pentaerythritol would be branched.

iv) Antimicrobials

An antimicrobial component may be added to impart antimicrobial activityto the fine fibers. The antimicrobial component is the component thatprovides at least part of the antimicrobial activity, i.e., it has atleast some antimicrobial activity for at least one microorganism. It ispreferably present in a large enough quantity to be released from thefine fibers and kill bacteria. It may also be biodegradable and/or madeor derived from renewable resources such as plants or plant products.Biodegradable antimicrobial components can include at least onefunctional linkage such as an ester or amide linkage that can behydrolytically or enzymatically degraded.

In some exemplary embodiments, a suitable antimicrobial component may beselected from a fatty acid monoester, a fatty acid di-ester, an organicacid, a silver compound, a quaternary ammonium compound, a cationic(co)polymer, an iodine compound, or combinations thereof. Other examplesof antimicrobial components suitable for use in the present inventioninclude those described in Applicants' co-pending application, U.S.Patent Application Publication No. 2008/0142023,-A1, and incorporated byreference herein in its entirety.

Certain antimicrobial components are uncharged and have an alkyl oralkenyl hydrocarbon chain containing at least 7 carbon atoms. For meltprocessing, preferred antimicrobial components have low volatility anddo not decompose under process conditions. The preferred antimicrobialcomponents contain no greater than 2 wt. % water, and more preferably nogreater than 0.10 wt. % (determined by Karl Fischer analysis). Moisturecontent is kept low in order to prevent hydrolysis of the aliphaticpolyester during extrusion.

When used, the antimicrobial component content (as it is ready to use)is typically at least 1 wt. %, 2 wt. %, 5 wt. %, 10 wt. % and sometimesgreater than 15 wt. %. In certain embodiments, for example applicationsin which a low strength is desired, the antimicrobial componentcomprises greater than 20 wt. %, greater than 25 wt. %, or even greaterthan 30 wt. % of the fine fibers.

Certain antimicrobial components are amphiphiles and may be surfaceactive. For example, certain antimicrobial alkyl monoglycerides aresurface active. For certain embodiments of the invention that includeantimicrobial components, the antimicrobial component is considereddistinct from a viscosity modifier component.

v) Particulate Phase

The fine fibers may further comprise organic and inorganic fillerspresent as either an internal particulate phase within the fibers, or asan external particulate phase on or near the surface of the fine fibers.For implantable applications biodegradable, resorbable, or bioerodibleinorganic fillers may be particularly appealing. These materials mayhelp to control the degradation rate of the polymer fine fibers. Forexample, many calcium salts and phosphate salts may be suitable.Exemplary biocompatible resorbable fillers include calcium carbonate,calcium sulfate, calcium phosphate, calcium sodium phosphates, calciumpotassium phosphates, tetra-calcium phosphate, alpha-tri-calciumphosphate, beta-tri-calcium phosphate, calcium phosphate apatite,octa-calcium phosphate, di-calcium phosphate, calcium carbonate, calciumoxide, calcium hydroxide, calcium sulfate di-hydrate, calcium sulfatehemihydrate, calcium fluoride, calcium citrate, magnesium oxide, andmagnesium hydroxide. A particularly suitable filler is tri-basic calciumphosphate (hydroxy apatite).

As described previously, these fillers and compounds can detrimentallyeffect physical properties of the web. Therefore, total additives otherthan the antishrink additive preferably are present at no more than 10%by weight, preferably no more than 5% by weight and most preferably nomore than 3% by weight.

vi) Surfactants

In certain exemplary embodiments, it may be desirable to add asurfactant to the mixture used to form the fine fibers. In particularexemplary embodiments, the surfactant may be selected from a nonionicsurfactant, an anionic surfactant, a cationic surfactant, a zwitterionicsurfactant, or combinations thereof. In additional exemplaryembodiments, the surfactant may be selected from a fluoro-organicsurfactant, a silicone-functional surfactant, an organic wax, or a saltof anionic surfactants such as dioctylsulfosuccinate.

In one presently preferred embodiment, the fine fibers may compriseanionic surfactants that impart durable hydrophilicity. Examples ofanionic surfactants suitable for use in the present invention includethose described in Applicants' co-pending publications, U.S. PatentApplication Publication No. US2008/0200890; and PCT InternationalPublication No. WO2009/152345, both incorporated by reference herein intheir entirety.

The fibers may also comprise anionic surfactants that impart durablehydrophilicity. Surfactants may be selected from the group of alkyl,alkaryl, alkenyl or aralkyl sulfate; alkyl, alkaryl, alkenyl or aralkylsulfonate; alkyl, alkaryl, alkenyl or aralkyl carboxylate; or alkyl,alkaryl, alkenyl or aralkyl phosphate surfactants. The compositions mayoptionally comprise a surfactant carrier which may aid processing and/orenhance the hydrophilic properties. The blend of the surfactant(s) andoptionally a surfactant carrieralkenyl, aralkyl, or alkarylcarboxylates, or combinations thereof. The viscosity modifier is presentin the melt extruded fiber in an amount sufficient to impart durablehydrophilicity to the fiber at its surface.

Preferably the surfactant is soluble in the carrier at extrusiontemperatures at the concentrations used. Solubility can be evaluated,for example, as the surfactant and carrier form a visually transparentsolution in a 1 cm path length glass vial when heated to extrusiontemperature (e.g. 150-190° C.). Preferably the surfactant is soluble inthe carrier at 150° C. More preferably the surfactant is soluble in thecarrier at less than 100° C. so that it can be more easily incorporatedinto the polymer melt. More preferably the surfactant is soluble in thecarrier at 25° C. so that no heating is necessary when pumping thesolution into the polymer melt. Preferably the surfactant is soluble inthe carrier at greater than 10% by weight, more preferably greater than20% by weight, and most preferably greater than 30% by weight in orderto allow addition of the surfactant without too much carrier present,which may plasticize the thermoplastic. Typically the surfactants arepresent at present in a total amount of at least 0.25 wt-%, preferablyat least 0.50 wt-%, more preferably at least 0.75 wt-%, based on thetotal weight of the composition. In certain embodiments, in which a veryhydrophilic web is desired, or a web that can withstand multipleassaults with aqueous fluid, the surfactant component comprises greaterthan 2 wt. %, greater than 3 wt. %, or even greater than 5 wt. % of thealiphatic polyester polymer composition. In certain embodiments, thesurfactants typically are present at 0.25 wt. % to 8 wt. % of thealiphatic polyester polymer composition. Typically, the surfactant ispresent at less than 10 weight %, preferably less than 8 weight %, morepreferably less than 7%, more preferably less than 6 weight %, morepreferably less than 3 weight %, and most preferably less than 2% byweight based on the combined weight of the aliphatic polyester.

The surfactant and optional carrier should be relatively free ofmoisture in order to facilitate extrusion and to prevent hydrolysis ofthe aliphatic polyester. Preferably the surfactant and optional carrier,either alone or in combination, comprise less than 5% water, morepreferably less than 2% water, even more preferably less than 1% water,and most preferably less than 0.5% water by weight as determined by aKarl-Fisher titration.

Certain classes of hydrocarbon, silicone, and fluorochemical surfactantshave each been described as useful for imparting hydrophilicity topolyolefins. These surfactants typically are contacted with thethermoplastic resin in one of two ways: (1) by topical application,e.g., spraying or padding or foaming, of the surfactants from aqueoussolution to the extruded nonwoven web or fiber followed by drying, or(2) by incorporation of the surfactant into the polyolefin melt prior toextrusion of the web. The latter is much preferable but is difficult tofind a surfactant that will spontaneously bloom to the surface of thefiber or film in sufficient amount to render the article hydrophilic. Aspreviously described, webs made hydrophilic by topical application of asurfactant suffer many drawbacks. Some are reported to also havediminished hydrophilicity after a single contact with aqueous media.Additional disadvantages to topical application of a surfactant toimpart hydrophilicity may include skin irritation from the surfactantitself, non-uniform surface and bulk hydrophilicity, and the additivecost resulting from the necessity of an added processing step in thesurfactant application. Incorporating one or more surfactants into tothe thermoplastic polymer as a melt additive alleviates the problemsassociated with topical application and in addition may provide a softer“hand” to the fabric or nonwoven web into which it is incorporated. Thechallenge as previously stated, is finding a surfactant that willreliably bloom to the surface of the article in sufficient amount toimpart hydrophilicity and then to remain properly oriented at thesurface to ensure durable hydrophilicity.

The fibers described herein remain hydrophilic and water absorbent afterrepeated insult with water, e.g. saturating with water, wringing out andallowing to dry. Preferred compositions of this invention include arelatively homogenous composition comprising at least one aliphaticpolyester resin (preferably polylactic acid), at least one alkylsulfate,alkylene sulfate, or aralkyl or alkaryl sulfate, carboxylate, orphosphate surfactant, typically in an amount of at 0.25 wt % to 8 wt %,and optionally a nonvolatile carrier in a concentration of 1 wt % to 8wt %, based on the weight of the aliphatic polyester as described inmore detail below.

Preferred porous fabric constructions of the present invention producedas knits, wovens, and nonwovens have apparent surface energies greaterthan 60 dynes/cm, and preferably greater than 70 dynes/cm when tested bythe Apparent Surface Energy Test disclosed in the Examples. Preferredporous fabric materials of this invention wet with water and thus havean apparent surface energy of greater than 72 dynes/cm (surface tensionof pure water). The most preferred materials of this invention instantlyabsorb water and remain water absorbent after aging for 10 days at 5°C., 23° C. and 45° C. Preferably, the nonwoven fabrics are“instantaneously absorbent” such that when a 200 ul drop of water isgently placed on an expanse of nonwoven on a horizontal surface it iscompletely absorbed in less than 10 seconds, preferably less than 5seconds and most preferably less than 3 seconds.

Preferred film constructions of the present invention are wettable byaqueous fluids and have a contact angle with deionized water of lessthan 40 degrees, preferably less than 30 degrees, and most preferablyless than 20 degrees when measured using a Tantec Contact Angle Meter(Shaumburg, Ill.), described as the half-angle technique in U.S. Pat.No. 5,268,733.

The present invention also discloses a method of making a relativelyhomogenous hydrophilic aliphatic polyester composition comprising ananionic surfactant and optionally a surfactant carrier by blending thesein a melt process, and forming a film, fiber, or foam.

The present invention also discloses a method of making a relativelyhomogenous hydrophilic aliphatic polyester composition comprising ananionic surfactant and optionally a surfactant carrier by blending theseto form a concentrate, blending the concentrate with additionalaliphatic polyester in a melt process, and forming a film, fiber, orfoam.

The present invention also discloses a method of making a relativelyhomogenous hydrophilic aliphatic polyester composition comprising ananionic surfactant and optionally a surfactant carrier by blending thesein a melt process, forming a film, fiber, or foam, and post heating thefilm, fiber or foam to a temperature greater than 50° C.

The present invention also discloses a method of making a relativelyhomogenous hydrophilic aliphatic polyester composition comprising ananionic surfactant and optionally a surfactant carrier by blending theseto form a concentrate, blending the concentrate with additionalaliphatic polyester in a melt process, forming a film, fiber, or foamand post heating the film, fiber, or foam to a temperature greater than50° C.

It is a significant advantage of the present invention that thesurfactant carrier and/or surfactant component in many embodimentsplasticizes the polyester component allowing for melt processing andsolvent casting of higher molecular weight polymers. Generally, weightaverage molecular weight (Mw) of the polymers is above the entanglementmolecular weight, as determined by a log-log plot of viscosity versusnumber average molecular weight (Mn). Above the entanglement molecularweight, the slope of the plot is about 3.4, whereas the slope of lowermolecular weight polymers is 1.

As used herein the term “surfactant” means an amphiphile (a moleculepossessing both polar and nonpolar regions which are covalently bound)capable of reducing the surface tension of water and/or the interfacialtension between water and an immiscible liquid. The term is meant toinclude soaps, detergents, emulsifiers, surface active agents, and thelike.

In certain preferred embodiments, the surfactants useful in thecompositions of the present invention are anionic surfactants selectedfrom the group consisting of alkyl, alkenyl, alkaryl and arakylsulfonates, sulfates, phosphonates, phosphates and mixtures thereof.Included in these classes are alkylalkoxylated carboxylates, alkylalkoxylated sulfates, alkylalkoxylated sulfonates, and alkyl alkoxylatedphosphates, and mixtures thereof. The preferred alkoxylate is made usingethylene oxide and/or propylene oxide with 0-100 moles of ethylene andpropylene oxide per mole of hydrophobe. In certain more preferredembodiments, the surfactants useful in the compositions of the presentinvention are selected from the group consisting of sulfonates,sulfates, phosphates, carboxylates and mixtures thereof. In one aspect,the surfactant is selected from (C8-C22) alkyl sulfate salts (e.g.,sodium salt); di(C8-C13 alkyl)sulfosuccinate salts; C8-C22 alkylsarconsinate; C8-C22 alkyl lactylates; and combinations thereof.Combinations of various surfactants can also be used. The anionicsurfactants useful in this invention are described in more detail belowand include surfactants with the following structure:

Where: R=is alkyl or alkylene of C8-C30, which is branched or straightchain, or C12-C30 aralkyl, and may be optionally substituted with 0-100alkylene oxide groups such as ethylene oxide, propylene oxide groups,oligameric lactic and/or glycolic acid or a combination thereof;

X=0 or 1;

M=is H, an alkali metal salts or an alkaline earth metal salt,preferably Li+, Na⁺, K⁺, or amine salts including tertiary andquaternary amines such as protonated triethanolamine,tetramethylammonium and the like.

n=1 or 2; and

a=1 when n=2 and a=2 when n=1. Preferably M may be Ca⁺⁺ or Mg⁺⁺,however, these are less preferred.

Examples include C8-C18 alkane sulfonates; C8-C18 secondary alkanesulfonates; alkylbenzene sulfonates such as dodecylbenzene sulfonate;C8-C18 alkyl sulfates; alkylether sulfates such as sodium trideceth-4sulfate, sodium laureth 4 sulfate, sodium laureth 8 sulfate (such asthose available from Stepan Company, Northfield Ill.), docusate sodiumalso known as dioctylsulfosuccinate, sodium salt; lauroyl lacylate andstearoyl lactylate (such as those available from RITA Corporation,Crystal Lake, Ill. under the PATIONIC tradename), and the like.Additional examples include stearyl phosphate (available as Sippostat0018 from Specialty Industrial Products, Inc., Spartanburg, S.C.);Cetheth-10 PPG-5 phosphate (Crodaphos SG, available from Croda USA,Edison N.J.); laureth-4 phosphate; and dilaureth-4 phosphate.

Exemplary anionic surfactants include, but are not limited to,sarcosinates, glutamates, alkyl sulfates, sodium or potassium alkylethsulfates, ammonium alkyleth sulfates, ammonium laureth-n-sulfates,laureth-n-sulfates, isethionates, glycerylether sulfonates,sulfosuccinates, alkylglyceryl ether sulfonates, alkyl phosphates,aralkyl phosphates, alkylphosphonates, and aralkylphosphonates. Theseanionic surfactants may have a metal or organic ammonium counterion.Certain useful anionic surfactants are selected from the groupconsisting of: sulfonates and sulfates such as alkyl sulfates,alkylether sulfates, alkyl sulfonates, alkylether sulfonates,alkylbenzene sulfonates, alkylbenzene ether sulfates,alkylsulfoacetates, secondary alkane sulfonates, secondaryalkylsulfates, and the like. Many of these can be represented by theformulas:R₂₆—(OCH₂CH₂)_(n6)(OCH(CH₃)CH₂)_(p2)-(Ph)_(a)-(OCH₂CH₂)_(m3)—(O)_(b)—SO³-M⁺andR²⁶—CH[SO³-M⁺]-R₂₇wherein: a and b=0 or 1; n6, p2, and m3=0-100 (preferably 0-20); R₂₆ isdefined as below provided at least one R₂₆ or R₂₇ is at least C8; R₂₇ isa (C1-C12)alkyl group (saturated straight, branched, or cyclic group)that may be optionally substituted by N, O, or S atoms or hydroxyl,carboxyl, amide, or amine groups; Ph=phenyl; and M⁺ is a cationiccounterion such as H, Na, K, Li, ammonium, or a protonated tertiaryamine such as triethanolamine or a quaternary ammonium group.

In the formula above, the ethylene oxide groups (i.e., the “n6” and “m3”groups) and propylene oxide groups (i.e., the “p2” groups) can occur inreverse order as well as in a random, sequential, or block arrangement.R₂₆ may be an alkylamide group such as R₂₈—C(O)N(CH₃)CH₂CH₂— as well asester groups such as —OC(O)—CH₂— wherein R₂₈ is a (C8-C22)alkyl group(branched, straight, or cyclic group). Examples include, but are notlimited to: alkyl ether sulfonates, including lauryl ether sulfates(such as POLYSTEP B12 (n=3-4, M=sodium) and B22 (n=12, M=ammonium)available from Stepan Company, Northfield, Ill.) and sodium methyltaurate (available under the trade designation NIKKOL CMT30, NikkoChemicals Co., Tokyo, Japan); secondary alkane sulfonates, includingsodium (C14-C17)secondary alkane sulfonates (alpha-olefin sulfonates)(such as Hostapur SAS available from Clariant Corp., Charlotte, N.C.);methyl-2-sulfoalkyl esters such as sodium methyl-2-sulfo(C12-16)esterand disodium 2-sulfo(C12-C16)fatty acid (available from Stepan Company,Northfield, Ill. under the trade designation ALPHASTEP PC-48);alkylsulfoacetates and alkylsulfosuccinates available as sodiumlaurylsulfoacetate (under the trade designation LANTHANOL LAL, StepanCompany, Northfield, Ill.) and disodiumlaurethsulfosuccinate (STEPANMILDSL3, Stepan Company, Northfield, Ill.); alkylsulfates such asammoniumlauryl sulfate (available under the trade designation STEPANOLAM from Stepan Company, Northfield, Ill.); dialkylsulfosuccinates suchas dioctylsodiumsulfosuccinate (available as Aerosol OT from CytecIndustries, Woodland Park, N.J.).

Suitable anionic surfactants also include phosphates such as alkylphosphates, alkylether phosphates, aralkylphosphates, and aralkyletherphosphates. Many may be represented by the formula:[R₂₆-(Ph)_(a)-O(CH₂CH₂O)_(n6)(CH₂CH(CH₃)O)_(p2)]_(q2)—P(O)[O-M⁺ ]r,wherein: Ph, R₂₆, a, n6, p2, and M are defined above; r is 0-2; andq2=1-3; with the proviso that when q2=1, r=2, and when q2=2, r=1, andwhen q2=3, r=0. As above, the ethylene oxide groups (i.e., the “n6”groups) and propylene oxide groups (i.e., the “p2” groups) can occur inreverse order as well as in a random, sequential, or block arrangement.Examples include a mixture of mono-, di- andtri-(alkyltetraglycolether)-o-phosphoric acid esters generally referredto as trilaureth-4-phosphate (available under the trade designationHOSTAPHAT 340KL from Clariant Corp.); as well as PPG-5 ceteth 10phosphate (available under the trade designation CRODAPHOS SG from CrodaInc., Parsipanny, N.J.), and mixtures thereof. In some embodiments, whenused in the composition, the surfactants are present in a total amountof at least 0.25 wt.-%, at least 0.5 wt-%, at least 0.75 wt-%, at least1.0 wt-%, or at least 2.0 wt-%, based on the total weight of thecomposition. In certain embodiments, in which a very hydrophilic web isdesired, or a web that can withstand multiple assaults with aqueousfluid, the surfactant component comprises greater than 2 wt. %, greaterthan 3 wt. %, or even greater than 5 wt. % of the degradable aliphaticpolyester polymer composition.

In other embodiments, the surfactants are present in a total amount ofno greater than 20 wt. %, no greater than 15 wt. %, no greater than 10wt. %, or no greater than 8 wt. %, based on the total weight of theready to use composition.

Preferred surfactants have a melting point of less than 200° C.,preferably less than 190° C., more preferably less than 180° C., andeven more preferably less than 170° C.

For melt processing, preferred surfactant components have low volatilityand do not decompose appreciably under process conditions. The preferredsurfactants contain less than 10 wt. % water, preferably less than 5%water, and more preferably less than 2 wt. % and even more preferablyless than 1% water (determined by Karl Fischer analysis). Moisturecontent is kept low in order to prevent hydrolysis of the aliphaticpolyester or other hydrolytically sensitive compounds in thecomposition, which will help to give clarity to extruded films or finefibers.

It can be particularly convenient to use a surfactant predissolved in anon-volatile carrier. Importantly, the carrier is typically thermallystable and can resist chemical breakdown at processing temperatureswhich may be as high as 150° C., 180° ° C., 200° C.° C., 250° C., oreven as high as 250° C. In a preferred embodiment, the surfactantcarrier is a liquid at 23° C.

Preferred carriers also may include low molecular weight esters ofpolyhydric alcohols such as triacetin, glyceryl caprylate/caprate,acetyltributylcitrate, and the like.

The solubilizing liquid carriers may alternatively be selected fromnon-volatile organic solvents. For purposes of the present invention, anorganic solvent is considered to be nonvolatile if greater than 80% ofthe solvent remains in the composition throughout the mixing and meltprocesses. Because these liquids remain in the melt processablecomposition, they function as plasticizers, generally lowering the glasstransition temperature of the composition.

Since the carrier is substantially nonvolatile it will in large partremain in the composition and may function as an organic plasticizer. Asused herein a plasticizer is a compound which when added to the polymercomposition results in a decrease in the glass transition temperature.Possible surfactant carriers include compounds containing one or morehydroxyl groups, and particularly glycols such glycerin; 1,2pentanediol; 2,4 diethyl-1,5 pentanediol; 2-methyl-1,3-propanediol; aswell as monofunctional compounds such 3-methoxy-methylbutanol (“MMB”).Additional examples of nonvolatile organic plasticizers includepolyethers, including polyethoxylated phenols such as Pycal 94(phenoxypolyethyleneglycol); alkyl, aryl, and aralkyl ether glycols(such as those sold under the Dowanol™ tradename by Dow ChemicalCompany, Midland Mich.) including but not limited to propyeleneglycolmonobutyl ether (Dowanol PnB), tripropyleneglycol monobutyl ether(Dowanol TPnB), dipropyeleneglycol monobutyl ether (Dowanol DPnB),propylene glycol monophenyl ether (Dowanol PPH), and propylene glycolmonomethyl ether (Dowanol PM); polyethoxylated alkyl phenols such asTriton X35 and Triton X102 (available from Dow Chemical Company, MidlandMich.); mono or polysubstituted polyethylene glycols such as PEG 400diethylhexanoate (TegMer 809, available from CP Hall Company), PEG 400monolaurate (CHP-30N available from CP Hall Company) and PEG 400monooleate (CPH-41N available from CP Hall Company); amides includinghigher alkyl substituted N-alkyl pyrrolidones such asN-octylpyrrolidone; sulfonamides such as N-butylbenzene sulfonamide(available from CP Hall Company); triglycerides; citrate esters; estersof tartaric acid; benzoate esters (such as those available from VelsicolChemical Corp., Rosemont Ill. under the Benzoflex tradename) includingdipropylene glycoldibenzoate (Benzoflex 50) and diethylene glycoldibenzoate; benzoic acid diester of 2,2,4 trimethyl 1,3 pentane diol(Benzoflex 354), ethylene glycol dibenzoate, tetraetheyleneglycoldibenzoate, and the like; polyethylene glycols and ethylene oxidepropylene oxide random and block copolymers having a molecular weightless than 10,000 daltons, preferably less than about 5000 daltons, morepreferably less than about 2500 daltons; and combinations of theforegoing. As used herein the term polyethylene glycols refer to glycolshaving 26 alcohol groups that have been reacted with ethylene oxide or a2 haloethanol.

Preferred polyethylene glycols are formed from ethylene glycol,propylene glycol, glycerin, trimethylolpropane, pentaerithritol, sucroseand the like. Most preferred polyethylene glycols are formed fromethylene glycol, propylene glycol, glycerin, and trimethylolpropane.Polyalkylene glycols such as polypropylene glycol, polytetramethyleneglycol, or random or block copolymers of C2 C4 alkylene oxide groups mayalso be selected as the carrier. Polyethylene glycols and derivativesthereof are presently preferred. It is important that the carriers becompatible with the polymer. For example, it is presently preferred touse non-volatile non-polymerizable plasticizers that have less than 2nucleophilic groups, such as hydroxyl groups, when blended with polymershaving acid functionality, since compounds having more than twonucleophilic groups may result in crosslinking of the composition in theextruder at the high extrusion temperatures. Importantly, thenon-volatile carriers preferably form a relatively homogeneous solutionwith the aliphatic polyester polymer composition in the extruder, andremain a relatively homogeneous composition upon cooling, such that theextruded composition is relatively uniform in surfactant concentration.The preferred hydrophilic additive surfactants of the present inventionallow for adhesive, thermal, and/or ultrasonic bonding of fabrics andfilms made thereof. The embodiments comprising nonanionic surfactantsare particularly suitable for use in surgical drapes and gowns due totheir unique wetting properties. For example, the polylacticacid/surfactant compositions have durable hydrophilicity as describedherein. Non-woven web and sheets comprising the inventive compositionshave good tensile strength; can be heat sealed to form strong bondsallowing specialty drape fabrication; can be made from renewableresources which can be important in disposable products; and can havehigh surface energy to allow wettability and fluid absorbency in thecase of non-wovens (as measured for nonwovens using the Apparent SurfaceEnergy test and absorbing water); and for films the contact angles oftenare less than 50 degrees, preferably less than 30 degrees, and mostpreferably less than 20 degrees when the contact angles are measuredusing distilled water on a flat film using the half angle techniquedescribed in U.S. Pat. No. 5,268,733 and a Tantec Contact Angle Meter,Model CAM-micro, Schamberg, Ill. In order to determine the contact angleof materials other than films, a film of the exact same compositionshould be made by solvent casting.

The processing temperature is sufficient to mix the biodegradablealiphatic polyester and surfactant, and allow extruding the compositionas a film. Films made with the compositions described herein haveproperties that are desirable in applications such as food wrap, e.g.,transparent (not hazy) and being free of oily residue on the surface(which might indicate phase separation of components from the polymermatrix).

The compositions may be solvent cast into a film. The ingredients of thecomposition are typically dissolved or at least partially solvated, andthoroughly mixed in a suitable solvent which is then cast on a surfaceand allowed to evaporate, leaving solids comprising the hydrophilicdurable resin composition.

viii) Other Optional Additives

Plasticizers may be used with the aliphatic polyester thermoplastic andinclude, for example, glycols such glycerin; propylene glycol,polyethoxylated phenols, mono or polysubstituted polyethylene glycols,higher alkyl substituted N-alkyl pyrrolidones, sulfonamides,triglycerides, citrate esters, esters of tartaric acid, benzoate esters,polyethylene glycols and ethylene oxide propylene oxide random and blockcopolymers having a molecular weight less than 10,000 daltons,preferably less than about 5000 daltons, more preferably less than about2500 daltons; and combinations thereof.

Other additional components include antioxidants, colorants such as dyesand/or pigments, antistatic agents, fluorescent brightening agents, odorcontrol agents, perfumes and fragrances, active ingredients to promotewound healing or other dermatological activity, combinations thereof,and the like.

As described previously, these fillers and additional compounds candetrimentally effect physical properties of the web. Therefore, totaladditives other than the antishrink additive preferably are present atno more than 10% by weight, preferably no more than 5% by weight andmost preferably no more than 3% by weight.

C. Methods of Making Dimensionally Stable Nonwoven Fibrous Webs

Exemplary processes that are capable of producing oriented fine fibersinclude: oriented film filament formation, melt-spinning, plexifilamentformation, spunbonding, wet spinning, and dry spinning. Suitableprocesses for producing oriented fibers are also known in the art (see,for example, Ziabicki, Andrzej, Fundamentals of Fibre Formation: TheScience of Fibre Spinning and Drawing, Wiley, London, 1976.).Orientation does not need to be imparted within a fiber during initialfiber formation, and may be imparted after fiber formation, mostcommonly using drawing or stretching processes.

The dimensionally stable nonwoven fibrous webs may include fine fibersthat are substantially sub-micrometer fibers, fine fibers that aresubstantially microfibers, or combinations thereof. In some exemplaryembodiments, a dimensionally stable nonwoven fibrous web may be formedof sub-micrometer fibers commingled with coarser microfibers providing asupport structure for the sub-micrometer nonwoven fibers. The supportstructure may provide the resiliency and strength to hold the finesub-micrometer fibers in the preferred low solidity form. The supportstructure could be made from a number of different components, eithersingly or in concert. Examples of supporting components include, forexample, microfibers, discontinuous oriented fibers, natural fibers,foamed porous cellular materials, and continuous or discontinuous nonoriented fibers.

Sub-micrometer fibers are typically very long, though they are generallyregarded as discontinuous. Their long lengths—with a length-to-diameterratio approaching infinity in contrast to the finite lengths of staplefibers—causes them to be better held within the matrix of microfibers.They are usually organic and polymeric and often of the molecularly samepolymer as the microfibers. As the streams of sub-micrometer fiber andmicrofibers merge, the sub-micrometer fibers become dispersed among themicrofibers. A rather uniform mixture may be obtained, especially in thex-y dimensions, or plane of the web, with the distribution in the zdimension being controlled by particular process steps such as controlof the distance, the angle, and the mass and velocity of the mergingstreams.

The relative amount of sub-micrometer fibers to microfibers included ina blended nonwoven composite fibrous web of the present disclosure canbe varied depending on the intended use of the web. An effective amount,i.e., an amount effective to accomplish desired performance, need not belarge in weight amount. Usually the microfibers account for at least oneweight percent and no greater than about 75 weight percent of the fibersof the web. Because of the high surface area of the microfibers, a smallweight amount may accomplish desired performance. In the case of websthat include very small microfibers, the microfibers generally accountfor at least 5 percent of the fibrous surface area of the web, and moretypically 10 or 20 percent or more of the fibrous surface area. Aparticular advantage of exemplary embodiments of the present inventionis the ability to present small-diameter fibers to a needed applicationsuch as filtration or thermal or acoustic insulation.

In one exemplary embodiment, a microfiber stream is formed and asub-micrometer fiber stream is separately formed and added to themicrofiber stream to form the dimensionally stable nonwoven fibrous web.In another exemplary embodiment, a sub-micrometer fiber stream is formedand a microfiber stream is separately formed and added to thesub-micrometer fiber stream to form the dimensionally stable nonwovenfibrous web. In these exemplary embodiments, either one or both of thesub-micrometer fiber stream and the microfiber stream is oriented. In anadditional embodiment, an oriented sub-micrometer fiber stream is formedand discontinuous microfibers are added to the sub-micrometer fiberstream, e.g. using a process as described in U.S. Pat. No. 4,118,531(Hauser).

In some exemplary embodiments, the method of making a dimensionallystable nonwoven fibrous web comprises combining the sub-micrometer fiberpopulation and the microfiber population into a dimensionally stablenonwoven fibrous web by mixing fiber streams, hydroentangling, wetforming, plexifilament formation, or a combination thereof. In combiningthe sub-micrometer fiber population with the microfiber population,multiple streams of one or both types of fibers may be used, and thestreams may be combined in any order. In this manner, nonwoven compositefibrous webs may be formed exhibiting various desired concentrationgradients and/or layered structures.

For example, in certain exemplary embodiments, the population ofsub-micrometer fibers may be combined with the population of microfibersto form an inhomogenous mixture of fibers. In other exemplaryembodiments, the population of sub-micrometer fibers may be formed as anoverlayer on an underlayer comprising the population of microfibers. Incertain other exemplary embodiments, the population of microfibers maybe formed as an overlayer on an underlayer comprising the population ofsub-micrometer fibers

In other exemplary embodiments, the nonwoven fibrous article may beformed by depositing the population of sub-micrometer fibers onto asupport layer, the support layer optionally comprising microfibers, soas to form a population of sub-micrometer fibers on the support layer orsubstrate. The method may comprise a step wherein the support layer,which optionally comprises polymeric microfibers, is passed through afiber stream of sub-micrometer fibers having a median fiber diameter ofno greater than 1 micrometer (μm). While passing through the fiberstream, sub-micrometer fibers may be deposited onto the support layer soas to be temporarily or permanently bonded to the support layer. Whenthe fibers are deposited onto the support layer, the fibers mayoptionally bond to one another, and may further harden while on thesupport layer.

In certain presently preferred embodiments, the sub-micrometer fiberpopulation is combined with an optional support layer that comprises atleast a portion of the microfiber population. In other presentlypreferred embodiments, the sub-micrometer fiber population is combinedwith an optional support layer and subsequently combined with at least aportion of the microfiber population.

1. Formation of Sub-Micrometer Fibers

A number of processes may be used to produce and deposit sub-micrometerfibers, including, but not limited to melt blowing, melt spinning, orcombination thereof. Particularly suitable processes include, but arenot limited to, processes disclosed in U.S. Pat. No. 3,874,886 (Levecqueet al.), U.S. Pat. No. 4,363,646 (Torobin), U.S. Pat. No. 4,536,361(Torobin), U.S. Pat. No. 5,227,107 (Dickenson et al.), U.S. Pat. No.6,183,670 (Torobin), U.S. Pat. No. 6,743,273 (Chung et al.), U.S. Pat.No. 6,800,226 (Gerking), and DE 19929709 C2 (Gerking), the entiredisclosures of which are incorporated herein by reference.

Suitable processes for forming sub-micrometer fibers also includeelectrospinning processes, for example, those processes described inU.S. Pat. No. 1,975,504 (Formhals), the entire disclosures of which areincorporated herein by reference. Other suitable processes for formingsub-micrometer fibers are described in U.S. Pat. No. 6,114,017(Fabbricante et al.); U.S. Pat. No. 6,382,526 B1 (Reneker et al.); andU.S. Pat. No. 6,861,025 B2 (Erickson et al.), the entire disclosures ofwhich are incorporated herein by reference.

The methods of making dimensionally stable nonwoven fibrous webs of thepresent disclosure may be used to form a sub-micrometer fiber componentcontaining fibers formed from any of the above-mentioned polymericmaterials. Typically, the sub-micrometer fiber forming method stepinvolves melt extruding a thermoformable material at a melt extrusiontemperature ranging from about 130° C. to about 350° C. A die assemblyand/or coaxial nozzle assembly (see, for example, the Torobin processreferenced above) comprises a population of spinnerets and/or coaxialnozzles through which molten thermoformable material is extruded. In oneexemplary embodiment, the coaxial nozzle assembly comprises a populationof coaxial nozzles formed into an array so as to extrude multiplestreams of fibers onto a support layer or substrate. See, for example,U.S. Pat. No. 4,536,361 (FIG. 2) and U.S. Pat. No. 6,183,670 (FIGS.1-2).

2. Formation of Microfibers

A number of processes may be used to produce and deposit microfibers,including, but not limited to, melt blowing, melt spinning, filamentextrusion, plexifilament formation, spunbonding, wet spinning, dryspinning, or a combination thereof. Suitable processes for formingmicrofibers are described in U.S. Pat. No. 6,315,806 (Torobin); U.S.Pat. No. 6,114,017 (Fabbricante et al.); U.S. Pat. No. 6,382,526 B1(Reneker et al.); and U.S. Pat. No. 6,861,025 B2 (Erickson et al.).Alternatively, a population of microfibers may be formed or converted tostaple fibers and combined with a population of sub-micrometer fibersusing, for example, using a process as described in U.S. Pat. No.4,118,531 (Hauser), the entire disclosure of which is incorporatedherein by reference. In certain exemplary embodiments, the population ofmicrofibers comprises a web of bonded microfibers, wherein bonding isachieved using thermal bonding, adhesive bonding, powdered binder,hydroentangling, needlepunching, calendering, or a combination thereof,as described below.

3. Apparatus for Forming Dimensionally Stable Nonwoven Fibrous Webs

A variety of equipment and techniques are known in the art for meltprocessing polymeric fine fibers. Such equipment and techniques aredisclosed, for example, in U.S. Pat. No. 3,565,985 (Schrenk et al.);U.S. Pat. No. 5,427,842 (Bland et. al.); U.S. Pat. Nos. 5,589,122 and5,599,602 (Leonard); and U.S. Pat. No. 5,660,922 (Henidge et al.).Examples of melt processing equipment include, but are not limited to,extruders (single and twin screw), Banbury mixers, and Brabenderextruders for melt processing the inventive fine fibers.

The (BMF) meltblowing process is one particular exemplary method offorming a nonwoven web of molecularly unoriented fibers where a polymerfluid, either molten or as a solution, is extruded through one or morerows of holes then impinged by a high velocity gas jet. The gas jet,typically heated air, entrains and draws the polymer fluid and helps tosolidify the polymer into a fiber. The solid fiber is then collected onsolid or porous surface as a nonwoven web. This process is described byVan Wente in “Superfine Thermoplastic Fibers”, Industrial EngineeringChemistry, vol. 48, pp. 1342-1346. An improved version of themeltblowing process is described by Buntin et al. as described in U.S.Pat. No. 3,849,241, and incorporated by reference herein in itsentirety.

As part of an exemplary BMF process for making fine fibers, athermoplastic polyester and polypropylene in a melt form may be mixed ina sufficient amount relative to an optional viscosity modifier to yieldfine fibers having average diameter characteristics as describedhereinabove. The ingredients of the fine fibers may be mixed in andconveyed through an extruder to yield a polymer, preferably withoutsubstantial polymer degradation or uncontrolled side reactions in themelt. The processing temperature is sufficient to mix the biodegradablealiphatic polyester viscosity modifier, and allow extruding the polymer.Potential degradation reactions include transesterification, hydrolysis,chain scission and radical chain define fibers, and process conditionsshould minimize such reactions.

The viscosity modifiers in the present disclosure need not be added tothe fiber extrusion process in a pure state. The viscosity modifiers maybe compounded with the aliphatic polyester, or other materials prior toextrusion. Commonly, when additives such as viscosity modifiers arecompounded prior to extrusion, they are compounded at a higherconcentration than desired for the final fiber. This high concentrationcompound is referred to as a master batch. When a master batch is used,the master batch will generally be diluted with pure polymer prior toentering the fiber extrusion process. Multiple additives may be presentin a masterbatch, and multiple master batches may be used in the fiberextrusion process.

Depending on the condition of the microfibers and sub-micrometer fibers,some bonding may occur between the fibers during collection. However,further bonding between the microfibers in the collected web is usuallyneeded to provide a matrix of desired coherency, making the web morehandleable and better able to hold the sub-micrometer fibers within thematrix (“bonding” fibers means adhering the fibers together firmly, sothey generally do not separate when the web is subjected to normalhandling).

Conventional bonding techniques using heat and pressure applied in apoint-bonding process or by smooth calender rolls can be used, thoughsuch processes may cause undesired deformation of fibers or compactionof the web. A more preferred technique for bonding the microfibers istaught in U.S. Patent Application Publication No. 2008/0038976.Apparatus for performing this technique is illustrated in FIGS. 1, 5 and6 of the drawings. In brief summary, as applied to the presentdisclosure, this preferred technique involves subjecting the collectedweb of microfibers and sub-micrometer fibers to a controlled heating andquenching operation that includes a) forcefully passing through the weba gaseous stream heated to a temperature sufficient to soften themicrofibers sufficiently to cause the microfibers to bond together atpoints of fiber intersection (e.g., at sufficient points of intersectionto form a coherent or bonded matrix), the heated stream being appliedfor a discrete time too short to wholly melt the fibers, and b)immediately forcefully passing through the web a gaseous stream at atemperature at least 50° C. no greater than the heated stream to quenchthe fibers (as defined in the above-mentioned U.S. Patent ApplicationPublication No. 2008/0038976, “forcefully” means that a force inaddition to normal room pressure is applied to the gaseous stream topropel the stream through the web; “immediately” means as part of thesame operation, i.e., without an intervening time of storage as occurswhen a web is wound into a roll before the next processing step). As ashorthand term this technique is described as the quenched flow heatingtechnique, and the apparatus as a quenched flow heater.

It has been found that the sub-micrometer fibers do not substantiallymelt or lose their fiber structure during the bonding operation, butremain as discrete microfibers with their original fiber dimensions.Without wishing to be bound by any particular theory, Applicant'sbelieve that sub-micrometer fibers have a different, less crystallinemorphology than microfibers, and we theorize that the limited heatapplied to the web during the bonding operation is exhausted indeveloping crystalline growth within the sub-micrometer fibers beforemelting of the sub-micrometer fibers occurs. Whether this theory iscorrect or not, bonding of the microfibers without substantial meltingor distortion of the sub-micrometer fibers does occur and may bebeneficial to the properties of the finished web.

A variation of the described method, taught in more detail in theaforementioned U.S. Patent Application Publication No. 2008/0038976,takes advantage of the presence of two different kinds of molecularphases within microfibers—one kind called crystallite-characterizedmolecular phases because of a relatively large presence ofchain-extended, or strain-induced, crystalline domains, and a secondkind called amorphous-characterized phases because of a relatively largepresence of domains of lower crystalline order (i.e., notchain-extended) and domains that are amorphous, though the latter mayhave some order or orientation of a degree insufficient forcrystallinity. These two different kinds of phases, which need not havesharp boundaries and can exist in mixture with one another, havedifferent kinds of properties, including different melting and/orsoftening characteristics: the first phase characterized by a largerpresence of chain-extended crystalline domains melts at a temperature(e.g., the melting point of the chain-extended crystalline domain) thatis higher than the temperature at which the second phase melts orsoftens (e.g., the glass transition temperature of the amorphous domainas modified by the melting points of the lower-order crystallinedomains).

In the stated variation of the described method, heating is at atemperature and for a time sufficient for the amorphous-characterizedphase of the fibers to melt or soften while thecrystallite-characterized phase remains unmelted. Generally, the heatedgaseous stream is at a temperature greater than the onset meltingtemperature of the polymeric material of the fibers. Following heating,the web is rapidly quenched as discussed above.

Treatment of the collected web at such a temperature is found to causethe microfibers to become morphologically refined, which is understoodas follows (we do not wish to be bound by statements herein of our“understanding,” which generally involve some theoreticalconsiderations). As to the amorphous-characterized phase, the amount ofmolecular material of the phase susceptible to undesirable(softening-impeding) crystal growth is not as great as it was beforetreatment. The amorphous-characterized phase is understood to haveexperienced a kind of cleansing or reduction of molecular structure thatwould lead to undesirable increases in crystallinity in conventionaluntreated fibers during a thermal bonding operation. Treated fibers ofcertain exemplary embodiments of the present invention may be capable ofa kind of “repeatable softening,” meaning that the fibers, andparticularly the amorphous-characterized phase of the fibers, willundergo to some degree a repeated cycle of softening and resolidifyingas the fibers are exposed to a cycle of raised and lowered temperaturewithin a temperature region lower than that which would cause melting ofthe whole fiber.

In practical terms, repeatable softening is indicated when a treated web(which already generally exhibits a useful bonding as a result of theheating and quenching treatment) can be heated to cause furtherautogenous bonding of the fibers. The cycling of softening andresolidifying may not continue indefinitely, but it is generallysufficient that the fibers may be initially bonded by exposure to heat,e.g., during a heat treatment according to certain exemplary embodimentsof the present invention, and later heated again to cause re-softeningand further bonding, or, if desired, other operations, such ascalendering or re-shaping. For example, a web may be calendered to asmooth surface or given a nonplanar shape, e.g., molded into a facemask, taking advantage of the improved bonding capability of the fibers(though in such cases the bonding is not limited to autogenous bonding).

While the amorphous-characterized, or bonding, phase has the describedsoftening role during web-bonding, calendering, shaping or other likeoperation, the crystallite-characterized phase of the fiber also mayhave an important role, namely to reinforce the basic fiber structure ofthe fibers. The crystallite-characterized phase generally can remainunmelted during a bonding or like operation because its melting point ishigher than the melting/softening point of the amorphous-characterizedphase, and it thus remains as an intact matrix that extends throughoutthe fiber and supports the fiber structure and fiber dimensions.

Thus, although heating the web in an autogenous bonding operation maycause fibers to weld together by undergoing some flow and coalescence atpoints of fiber intersection, the basic discrete fiber structure issubstantially retained over the length of the fibers betweenintersections and bonds; preferably, the cross-section of the fibersremains unchanged over the length of the fibers between intersections orbonds formed during the operation. Similarly, although calendering of aweb may cause fibers to be reconfigured by the pressure and heat of thecalendering operation (thereby causing the fibers to permanently retainthe shape pressed upon them during calendering and make the web moreuniform in thickness), the fibers generally remain as discrete fiberswith a consequent retention of desired web porosity, filtration, andinsulating properties.

One aim of the quenching is to withdraw heat before undesired changesoccur in the microfibers contained in the web. Another aim of thequenching is to rapidly remove heat from the web and the fibers andthereby limit the extent and nature of crystallization or molecularordering that will subsequently occur in the fibers. By rapid quenchingfrom the molten/softened state to a solidified state, theamorphous-characterized phase is understood to be frozen into a morepurified crystalline form, with reduced molecular material that caninterfere with softening, or repeatable softening, of the fibers. Forsome purposes, quenching may not be absolutely required though it isstrongly preferred for most purposes.

To achieve quenching the mass is desirably cooled by a gas at atemperature at least 50° C. no greater than the nominal melting point;also the quenching gas is desirably applied for a time on the order ofat least one second (the nominal melting point is often stated by apolymer supplier; it can also be identified with differential scanningcalorimetry, and for purposes herein, the “Nominal Melting Point” for apolymer is defined as the peak maximum of a second-heat, total-heat-flowDSC plot in the melting region of a polymer if there is only one maximumin that region; and, if there are more than one maximum indicating morethan one melting point (e.g., because of the presence of two distinctcrystalline phases), as the temperature at which the highest-amplitudemelting peak occurs). In any event the quenching gas or other fluid hassufficient heat capacity to rapidly solidify the fibers.

One advantage of certain exemplary embodiments of the present inventionmay be that the sub-micrometer fibers held within a microfiber web maybe better protected against compaction than they would be if present inan all-sub-micrometer fiber layer. The microfibers are generally larger,stiffer and stronger than the sub-micrometer fibers, and they can bemade from material different from that of the microfibers. The presenceof the microfibers between the sub-micrometer fibers and an objectapplying pressure may limit the application of crushing force on thesub-micrometer fibers. Especially in the case of sub-micrometer fibers,which can be quite fragile, the increased resistance against compactionor crushing that may be provided by certain exemplary embodiments of thepresent invention offers an important benefit. Even when webs accordingto the present disclosure are subjected to pressure, e.g., by beingrolled up in jumbo storage rolls or in secondary processing, webs of thepresent disclosure may offer good resistance to compaction of the web,which could otherwise lead to increased pressure drop and poor loadingperformance for filters. The presence of the microfibers also may addother properties such as web strength, stiffness and handlingproperties.

The diameters of the fibers can be tailored to provide neededfiltration, acoustic absorption, and other properties. For example itmay be desirable for the microfibers to have a median diameter of 5 to50 micrometers (μm) and the sub-micrometer fibers to have a mediandiameter from 0.1 μm to no greater than 1 μm, for example, 0.9 μm.Preferably the microfibers have a median diameter between 5 μm and 50μm, whereas the sub-micrometer fibers preferably have a median diameterof 0.5 μm to no greater than 1 μm, for example, 0.9 μm.

As previously stated, certain exemplary embodiments of the presentinvention may be particularly useful to combine very small microfibers,for example ultrafine microfibers having a median diameter of from 1 μmto about 2 μm, with the sub-micrometer fibers. Also, as discussed above,it may be desirable to form a gradient through the web, e.g., in therelative proportion of sub-micrometer fibers to microfibers over thethickness of the web, which may be achieved by varying processconditions such as the air velocity or mass rate of the sub-micrometerfiber stream or the geometry of the intersection of the microfiber andsub-micrometer fiber streams, including the distance of the die from themicrofiber stream and the angle of the sub-micrometer fiber stream. Ahigher concentration of sub-micrometer fibers near one edge of adimensionally stable nonwoven fibrous web according to the presentdisclosure may be particularly advantageous for gas and/or liquidfiltration applications.

In preparing microfibers or sub-micrometer fibers according to variousembodiments of the present disclosure, different fiber-forming materialsmay be extruded through different orifices of a meltspinning extrusionhead or meltblowing die so as to prepare webs that comprise a mixture offibers. Various procedures are also available for electrically charginga dimensionally stable nonwoven fibrous web to enhance its filtrationcapacity: see e.g., U.S. Pat. No. 5,496,507 (Angadjivand).

If a web could be prepared from the sub-micrometer fibers themselves,such a web would be flimsy and weak. However, by incorporating thepopulation of sub-micrometer fibers with a population of microfibers ina coherent, bonded, oriented composite fibrous structure, a strong andself-supporting web or sheet material can be obtained, either with orwithout an optional support layer.

In addition to the foregoing methods of making a dimensionally stablenonwoven fibrous web, one or more of the following process steps may becarried out on the web once formed:

(1) advancing the dimensionally stable nonwoven fibrous web along aprocess pathway toward further processing operations;

(2) bringing one or more additional layers into contact with an outersurface of the sub-micrometer fiber component, the microfiber component,and/or the optional support layer;

(3) calendering the dimensionally stable nonwoven fibrous web;

(4) coating the dimensionally stable nonwoven fibrous web with a surfacetreatment or other composition (e.g., a fire retardant composition, anadhesive composition, or a print layer);

(5) attaching the dimensionally stable nonwoven fibrous web to acardboard or plastic tube;

(6) winding-up the dimensionally stable nonwoven fibrous web in the formof a roll;

(7) slitting the dimensionally stable nonwoven fibrous web to form twoor more slit rolls and/or a plurality of slit sheets;

(8) placing the dimensionally stable nonwoven fibrous web in a mold andmolding the dimensionally stable nonwoven fibrous web into a new shape;

(9) applying a release liner over an exposed optional pressure-sensitiveadhesive layer, when present; and

(10) attaching the dimensionally stable nonwoven fibrous web to anothersubstrate via an adhesive or any other attachment device including, butnot limited to, clips, brackets, bolts/screws, nails, and straps.

D. Articles Formed from Dimensionally Stable Nonwoven Fibrous Webs

The present disclosure is also directed to methods of using thedimensionally stable nonwoven fibrous webs of the present disclosure ina variety of applications. In a further aspect, the disclosure relatesto an article comprising a dimensionally stable nonwoven fibrous webaccording to the present disclosure. In exemplary embodiments, thearticle may be used as a gas filtration article, a liquid filtrationarticle, a sound absorption article, a thermal insulation article, asurface cleaning article, a cellular growth support article, a drugdelivery article, a personal hygiene article, a dental hygiene article,a surgical drape, a surgical equipment isolation drape, a medicalisolation drape, a surgical gown, a medical gown, healthcare patientgowns and attire, an apron or other apparel, a sterilization wrap, awipe, agricultural fabrics, food packaging, packaging, a tape backing,or a wound dressing article.

For example, a dimensionally stable nonwoven fibrous web of the presentdisclosure may be advantageous in gas filtration applications due to thereduced pressure drop that results from lower Solidity. Decreasing theSolidity of a sub-micrometer fiber web will generally reduce itspressure drop. Lower pressure drop increase upon particulate loading oflow Solidity sub-micrometer dimensionally stable nonwoven fibrous web ofthe present disclosure may also result. Current technology for formingparticle-loaded sub-micrometer fibers results in much higher pressuredrop than for coarser microfiber webs, partially due to the higherSolidity of the fine sub-micrometer fiber web.

In addition, the use of sub-micrometer fibers in gas filtration may beparticularly advantageous due to the improved particle captureefficiency that sub-micrometer fibers may provide. In particular,sub-micrometer fibers may capture small diameter airborne particulatesbetter than coarser fibers. For example, sub-micrometer fibers may moreefficiently capture airborne particulates having a dimension smallerthan about 1000 nanometers (nm), more preferably smaller than about 500nm, even more preferably smaller than about 100 nm, and most preferablybelow about 50 nm. Gas filters such as this may be particularly usefulin personal protection respirators; heating, ventilation and airconditioning (HVAC) filters; automotive air filters (e.g. automotiveengine air cleaners, automotive exhaust gas filtration, automotivepassenger compartment air filtration); and other gas-particulatefiltration applications.

Liquid filters containing sub-micrometer fibers in the form ofdimensionally stable nonwoven fibrous webs of the present disclosure mayalso have the advantage of improved depth loading while maintainingsmall pore size for capture of sub-micrometer, liquid-borneparticulates. These properties improve the loading performance of thefilter by allowing the filter to capture more of the challengeparticulates without plugging.

A fiber-containing dimensionally stable nonwoven fibrous web of thepresent disclosure may also be a preferred substrate for supporting amembrane. The low Solidity fine web could act a both a physical supportfor the membrane, but also as a depth pre-filter, enhancing the life ofthe membrane. The use of such a system could act as a highly effectivesymmetric or asymmetric membrane. Applications for such membranesinclude ion-rejection, ultrafiltration, reverse osmosis, selectivebinding and/or adsorption, and fuel cell transport and reaction systems.

Dimensionally stable nonwoven fibrous webs of the present disclosure mayalso be useful synthetic matrices for promoting cellular growth. Theopen structure with fine sub-micrometer fibers may mimic naturallyoccurring systems and promotes more in vivo-like behavior. This is incontrast to current products (such as Donaldson ULTRA-WEB™ SyntheticECM, available from Donaldson Corp., Minneapolis, Minn.) where highSolidity fiber webs act as a synthetic support membrane, with little orno penetration of cells within the fiber matrix.

The structure provided by the dimensionally stable nonwoven fibrous websof the present disclosure may also be an effective wipe for surfacecleaning, where the fine sub-micrometer fibers form a soft wipe, whilelow Solidity may have the advantage of providing a reservoir forcleaning agents and high pore volume for trapping debris. Thehydrophilic dimensionally stable nonwoven fibrous webs of the presentinvention may be used as absorbent dry wipes or as so called wet wipeswhich typically have cleaning agents such as surfactants in a volatilesolvent. They also may be very useful as cosmetic wipes for use on skinand mucosal tissue.

For acoustic and thermal insulation applications, providing the finesub-micrometer fibers in a low Solidity form improves acousticabsorbance by exposing more of the surface area of the sub-micrometerfibers, as well as specifically improving low frequency acousticabsorbance by allowing for a thicker web for a given basis weight. Inthermal insulation applications in particular, a fine sub-micrometerfiber insulation containing sub-micrometer fibers would have a soft feeland high drapability, while providing a very low Solidity web fortrapping insulating air. In some embodiments, the nonwoven web maycomprise hollow fibers or filaments or fibers containing gas voids. Aspunbond process may be used to prepare nonwoven fabric of continuous,hollow fibers or filaments containing voids that are particularly usefulfor acoustic and thermal insulation; the voids may allow for animprovement in acoustic damping, reduction in thermal conductivity, anda reduction in weight of the dimensionally stable nonwoven fibrous websand articles made therefrom.

In some embodiments of a use of such an acoustic and/or thermalinsulation article, an entire area may be surrounded by a dimensionallystable nonwoven fibrous web prepared according to embodiments of thepresent disclosure, provided alone or on a support layer. The supportstructure and the fibers comprising the dimensionally stable nonwovenfibrous web may, but need not be homogeneously dispersed within oneanother. There may be advantages in cushioning, resiliency and filterloading for asymmetric loading to provide ranges of pore sizes, higherdensity regions, exterior skins or flow channels.

The fine fibers are particularly useful for making absorbent orrepellent aliphatic polyester nonwoven gowns and film laminate drapesused in surgery as well as personal care absorbents such as femininehygiene pads, diapers, incontinence pads, wipes, fluid filters,insulation and the like.

Various embodiments of the presently disclosed invention also providesuseful articles made from fabrics and webs of fine fibers includingmedical drapes, medical gowns, aprons, filter media, industrial wipesand personal care and home care products such as diapers, facial tissue,facial wipes, wet wipes, dry wipes, disposable absorbent articles andgarments such as disposable and reusable garments including infantdiapers or training pants, adult incontinence products, feminine hygieneproducts such as sanitary napkins and panty liners and the like. Thefine fibers of this invention also may be useful for producing thermalinsulation for garments such as coats, jackets, gloves, cold weatherpants, boots, and the like as well as acoustical insulation.

In yet another aspect, this invention provides multi-layer, aqueousliquid-absorbent articles comprising an aqueous media impervious backingsheet. For example, importantly some surgical drapes are liquidimpervious to prevent liquid that is absorbed into the top sheet fromwicking through to the skin surface where it would be contaminated withbacteria present on the skin. In other embodiments the construction mayfurther comprise an aqueous media permeable topsheet, and an aqueousliquid-absorbent (i.e., hydrophilic) layer constructed of theabove-described web or fabric juxtaposed there between useful, forinstance, in constructing disposable diapers, wipes or towels, sanitarynapkins, and incontinence pads.

In yet another aspect, a single or multi-layer water and body fluidrepellent article such as a surgical or medical gown or apron can beformed at least in part of a web of fine fibers described herein, andhaving aqueous fluid repellent properties. For example, an SMS web maybe formed having fine fibers in at least the M (melt blown, blowmicrofiber) layer but they may also comprise the S (spunbond layer aswell). The M layer may have further incorporated therein a repellentadditive such as a fluorochemical. In this manner, the gown is renderedfluid repellent to avoid absorption of blood or other body fluids thatmay contain pathogenic microorganisms. Alternatively, the web may bepost treated with a repellent finish such as a fluorochemical. In yetanother aspect, a wrap may be formed that is used to wrap cleaninstruments prior to surgery or other procedure requiring sterile tools.These wraps allow penetration of sterilizing gasses such as steam,ethylene oxide, hydrogen peroxide, ozone, etc. but they do not allowpenetration of bacteria. The wraps may be made of a single ormulti-layer water repellent article such as a sterilization wrap whichcan be formed at least in part of a web of fine fibers described herein,and having aqueous fluid repellent properties. For example, a SMS, SMMS,or other nonwoven construction web may be formed having fine fibers inat least the M (melt blown, blown microfiber) layer but they may alsocomprise the S (spunbond layer as well). The M layer may have furtherincorporated therein or thereon a repellent additive such as afluorochemical. Preferred fluorochemicals comprise a perfluoroalkylgroup having at least 4 carbon atoms. These fluorochemicals may be smallmolecules, oligamers, or polymers. Suitable fluorochemicals may be foundin U.S. Pat. No. 6,127,485 (Klun at al.) and U.S. Pat. No. 6,262,180(Klun et al), the disclosures of which are incorporated by reference intheir entirety. Other suitable repellants may include fluorochemicalsand silicone fluids repellents disclosed in Applicants co-pendingpublication, PCT International Publication No. WO2009/152349, citingpriority to the foregoing application. In some instances hydrocarbontype repellents may be suitable. Suitable fluorochemicals and siliconesthat serve as repellent additives are described below.

A sterilization wrap constructed from such a single or multi-layerrepellent article described herein possesses all of the propertiesrequired of a sterilization wrap; i.e., permeability to steam orethylene oxide or other gaseous sterilant during sterilization (andduring drying or aeration) of the articles it encloses, repellency ofliquid water during storage to avoid contamination of the contents ofthe wrap by water-borne contaminants, and a tortuous path barrier tocontamination by air- or water-borne microbes during storage of thesterilized pack.

The fine fiber webs of exemplary embodiments of the presently disclosedinvention may be rendered more repellent by treatment with numerouscompounds. For example, the fabrics may be post web forming surfacetreatments which include paraffin waxes, fatty acids, bee's wax,silicones, fluorochemicals and combinations thereof. For example, therepellent finishes may be applied as disclosed in U.S. Pat. Nos.5,027,803; 6,960,642; and 7,199,197, all of which are incorporated byreference herein in its entirety. Repellent finishes may also be meltadditives such as those described in U.S. Pat. No. 6,262,180, which isincorporated by reference herein in its entirety.

Repellent Additive

Preferred fluorochemicals comprise a perfluoroalkyl group having atleast 4 carbon atoms. These fluorochemicals may be small molecules,oligamers, or polymers. Silicone fluid repellents also may be suitable.In some instances hydrocarbon-type repellents may also be suitable.

Classes of fluorochemical agents or compositions useful in thisinvention include compounds and polymers containing one or morefluoroaliphatic radicals, Rf. In general, fluorochemical agents orcompositions useful as a repellent additive comprise fluorochemicalcompounds or polymers containing fluoroaliphatic radicals or groups, Rf.The fluoroaliphatic radical, Rf, is a fluorinated, stable, inert,non-polar, preferably saturated, monovalent moiety which is bothhydrophobic and oleophobic. It can be straight chain, branched chain,or, if sufficiently large, cyclic, or combinations thereof, such asalkylcycloaliphatic radicals. The skeletal chain in the fluoroaliphaticradical can include catenary divalent oxygen atoms and/or trivalentnitrogen atoms bonded only to carbon atoms. Generally Rf will have 3 to20 carbon atoms, preferably 6 to about 12 carbon atoms, and will containabout 40 to 78 weight percent, preferably 50 to 78 weight percent,carbon-bound fluorine. The terminal portion of the Rf group has at leastone trifluoromethyl group, and preferably has a terminal group of atleast three fully fluorinated carbon atoms, e.g., CF₃CF₂CF₂—. Thepreferred Rf groups are fully or substantially fluorinated, as in thecase where Rf is perfluroalkyl, CnF₂n+1—.

Examples of such compounds include, for example, fluorochemicalurethanes, ureas, esters, amines (and salts thereof), amides, acids (andsalts thereof), carbodiimides, guanidines, allophanates, biurets, andcompounds containing two or more of these groups, as well as blends ofthese compounds.

Useful fluorochemical polymers containing Rf radicals include copolymersof fluorochemical acrylate and/or methacrylate monomers withco-polymerizable monomers, including fluorine-containing andfluorine-free monomers, such as methyl methacrylate, butyl acrylate,octadecyl methacrylate, acrylate and methacrylate esters ofpoly(oxyalkylene) polyol oligomers and polymers, e.g., poly(oxyethylene)glycol dimethacrylate, glycidyl methacrylate, ethylene, vinyl acetate,vinyl chloride, vinylidene chloride, vinylidene fluoride, acrylonitrile,vinyl chloroacetate, isoprene, chloroprene, styrene, butadiene,vinylpyridine, vinyl alkyl esters, vinyl alkyl ketones, acrylic andmethacrylic acid, 2-hydroxyethyl acrylate, N-methylolacrylamide,2-(N,N,N-trimethylammonium)ethyl methacrylate and the like.

The relative amounts of various comonomers which can be used with thefluorochemical monomer will generally be selected empirically, and willdepend on the substrate to be treated, the properties desire from thefluorochemical treatment, i.e., the degree of oil and/or waterrepellency desired, and the mode of application to the substrate.

Useful fluorochemical agents or compositions include blends of thevarious classes of fluorochemical compounds and/or polymers describedabove. Also, blends of these fluorochemical compounds or polymers withfluorine-free compounds, e.g., N-acyl aziridines, or fluorine-freepolymers, e.g., polyacrylates such as poly(methyl methacrylate) andpoly(methyl methacrylate-co-decyl acrylate), polysiloxanes and the like.

The fluorochemical agents or compositions can include non-interferingadjuvants such as wetting agents, emulsifiers, solvents (aqueous andorganic), dyes, biocides, fillers, catalysts, curing agents and thelike. The final fluorochemical agent or composition should contain, on asolids basis, at least about 5 weight percent, preferably at least about10 weight percent carbon-bound fluorine in the form of said Rf groups inorder to impart the benefits described in this invention. Suchfluorochemicals are generally known and commercially available asperfluoroaliphatic group bearing water/oil repellent agents whichcontain at least 5 percent by weight of fluorine, preferably 7 to 12percent of fluorine in the available formulations.

By the reaction of the perfluoroaliphatic thioglycols withdiisocyanates, there results perfluoroaliphatic group-bearingpolyurethanes. These products are normally applied in aqueous dispersionfor fiber treatment. Such reaction products are described in U.S. Pat.No. 4,054,592, incorporated herein by reference.

Another group of suitable compounds are perfluoroaliphatic group-bearingN-methylol condensation products. These compounds are described in U.S.Pat. No. 4,477,498, incorporated herein by reference where theemulsification of such products is dealt with in detail.

The perfluoroaliphatic group-bearing polycarbodimides are, e.g.,obtained by reaction of perfluoroaliphatic sulfonamide alkanols withpolyisocyanates in the presence of suitable catalysts. This class ofcompounds can be used by itself, but often is used with other Rf-groupbearing compounds, especially with (co)polymers. Thus, another group ofcompounds which can be used in dispersions is mentioned. Among thesecompounds all known polymers bearing fluoroaliphatic residues can beused, also condensation polymers, such as polyesters and polyamideswhich contain the corresponding perfluoroaliphatic groups, areconsidered but especially (co)polymers on the basis of e.g. Rf-acrylatesand Rf-methacrylates, which can contain different fluorine-free vinylcompounds as comonomers. In DE-A 2 310 801, these compounds arediscussed in detail. The manufacture of Rf-group bearingpolycarbodimides as well as the combination of these compounds with eachother is also described in detail.

Besides the aforementioned perfluoroaliphatic group-bearing agents,further fluorochemical components may be used, for example,Rf-group-bearing guanidines, U.S. Pat. No. 4,540,479, Rf-group-bearingallophanates, U.S. Pat. No. 4,606,737 and Rf-group-bearing biurets, U.S.Pat. No. 4,668,406, the disclosures which are incorporated herein byreference. These classes are mostly used in combination. Others includefluoroalkyl-substituted siloxanes, e.g., CF₃(CF₂)₆CH₂O(CH₂)₃Si(OC₂H₅)₃—.

The useful compounds show, in general, one or more perfluoroaliphaticresidues with preferably at least 4 carbon atoms, especially 4 to 14atoms each. An exemplary fluorochemical is a formulation of 70% solventsand 30% emulsified solid fluorochemical polymers. The formulationincludes as solvents 11% methyl isobutyl ketone, 6% ethylene glycol and53% water. The fluorochemical polymers are a 50/50 blend of 5/95copolymer of butyl acrylate and C₈F₁₇SO₂(CH₃)C₂H₄O—CCH═CH₂ prepared asdescribed in U.S. Pat. No. 3,816,229, incorporated herein by reference(see especially column 3, lines 66-68 and column 4, lines 1-11) for a10/90 copolymer. The second component of the 50/50 blend is a copolymerprepared from 1 mole of a tri-functional phenyl isocyanate (availablefrom Upjohn Company under the name PAPI), 2 moles ofC₈F₁₇N(CH₂CH₃)CH₂CH₂OH and 1 mole of stearyl alcohol prepared asdescribed in U.S. Pat. No. 4,401,780, incorporated herein by reference(see especially Table 1, C2 under footnote A). Emulsifiers used areconventional commercially available materials such as polyethoxylatedquaternary ammonium compounds (available under the name 5% Ethoquad18/25 from Akzo Chemie America) and 7.5% of a 50/50 mixture ofC₈F₁₇SO₂NHC₃H₆N(CH₃)₃C1 and a polyethoxylated sorbitan monooleate(available from ICI Limited under the name TWEEN 80). Suchfluorochemicals are non-yellowing and particularly non-irritating to theskin as well as providing articles that are stable having excellent longterm aging properties. Exemplary fluorochemicals are available under thetrade designations SCOTCHGARD, SCOTCH-RELEASE, and 3M BRAND TEXTILECHEMICAL and are commercially from the 3M Company. Other commerciallyavailable materials include materials that use fluorotelomer chemistrymaterials provided by DuPont (available from duPont deNemours andCompany, Wilmington, Del.).

Suitable silicones for use to obtain the low surface energy layers ofthe instant invention include any of the silicones known to thoseskilled in the art to provide water repellency and optionally oilrepellency to fibers and films. Silicone fluids typically consist oflinear polymers of rather low molecular weight, namely about4000-25,000. Most commonly the polymers are polydimethylsiloxanes.

For use as fluids with enhanced thermal stability, silicones containingboth methyl and phenyl groups are often used. Generally, the phenylgroups make up 10-45% of the total number of substituent groups present.Such silicones are generally obtained by hydrolysis of mixtures ofmethyl- and phenylchlorosilanes. Fluids for use in textile treatment mayincorporate reactive groups so that they may be cross-linked to give apermanent finish. Commonly, these fluids contain Si—H bonds (introducedby including methyldichlorosilane in the polymerization system) andcross-linking occurs on heating with alkali.

Examples of suitable silicones are those available from Dow-CorningCorporation such as C2-0563 and from General Electric Corporation suchas GE-SS4098. Especially preferred silicone finishes are disclosed inU.S. Pat. No. 5,045,387.

Articles that may be made of fine fibers or the dimensionally stablenonwoven fibrous webs of the present disclosure may include medicaldrapes and gowns, including surgical drapes, procedural drapes, plasticspecialty drapes, incise drapes, barrier drapes, barrier gowns, SMSgowns, and the like; sterilization wraps; wound dressings, woundabsorbents, and wound contact layers; surgical sponges use to absorbblood and body fluids during surgery; surgical implants; and othermedical devices. Articles made of the fine fibers may be solvent, heat,or ultrasonically welded together as well as being welded to othercompatible articles. The fine fibers may be used in conjunction withother materials to form constructions such as sheath/core materials,laminates, compound structures of two or more materials, or useful ascoatings on various medical devices. The fine fibers described hereinmay be useful in the fabrication of surgical sponges.

In certain embodiments, the dimensionally stable nonwoven fibrous web isa component of a surgical drape. As used herein a “surgical drape” is atextile that is used to cover the patient and/or instrumentation andother objects during invasive procedures such as surgery but includeother procedures such as urinary and vascular access catherization,spinal block placement, etc where maintaining a sterile field isdesirable. The drapes are most often provided sterile. The fiber webs ofthis invention can be sterilized by conventional methods such assterilizing gases including steam, ethylene oxide, hydrogen peroxide,ozone, combinations thereof, and the like. A significant advantage isthat the fine fiber webs can be sterilized by gamma irradiation withoutsignificant loss in physical properties.

The purpose of the drape is to provide a sterile surface and to containmicrobial contamination from the patient and/or equipment. Thus, thefine fiber web may be coated with an impervious film. Any suitable filmcan be used. When laminated to an impervious film the fine fiber webrendered hydrophilic as also described in Applicants' co-pendingpublication, PCT International Publication No. WO2009/152345 and PCTInternational Publication No. WO2009/152345, citing priority to theforegoing and filed on Jun. 11, 2009, each incorporated by referenceherein in their entirety; and may be constructed as described inco-pending PCT International Publication No. WO 2010/117612,incorporated by reference in its entirety. In this manner, the drape isabsorbent and still a barrier. Alternatively, the drape may beconstructed of a fine fiber-containing web which has been treated with arepellent additive as described above.

In certain embodiments the fiber web is a component of a surgical gown.As used herein a “surgical gown” is a textile that is used to cover theclinician during invasive procedures such as surgery. Additionally, thegowns may be used for many other procedures where the clinician wishesto protect themselves from contamination. The gowns are most oftenprovided sterile and may be sterilized as described above for thesurgical drapes. Typically the gown is constructed of a finefiber-containing web which may have been treated with the repellentadditive as described above. The purpose of the gown is to provide asterile surface and to contain microbial contamination from theclinician so that it does not contaminate a sterile field. Importantly,the gowns also may be used to protect the clinician from exposure toinfectious agents such as bacteria, spores, virus, mycobacterium etc.Thus, the fine fiber web may be coated with an impervious film. Anysuitable film can be used. Preferably, if a film is used it ismicroporous to allow moisture evaporation. Alternatively, the gown maybe constructed of a fine fiber containing web which has been treated tobe repellent additive as described above. In this manner, any blood orbody fluids that contact the gown are repelled and will not soak in tocontact the clinician.

When used, the preferred hydrophilic additive surfactants of the presentinvention allow for adhesive, thermal, and/or ultrasonic bonding offabrics and films made thereof. The fine fibers are particularlysuitable for use in surgical drapes and gowns. Non-woven web and sheetscomprising the fine fibers can be heat sealed to form strong bondsallowing specialty drape fabrication; can be made from renewableresources which can be important in disposable products; and can havehigh surface energy to allow wettability and fluid absorbency in thecase of non-wovens. In other applications, a low surface energy may bedesirable to impart fluid repellency.

It is believed that such non-woven materials can be sterilized by gammaradiation or electron beam without significant loss of physical strength(tensile strength for a 1 mil thick film does not decrease by more than20% and preferably by not more than 10% after exposure to 2.5 Mrad gammaradiation from a cobalt gamma radiation source and aged at 23° C.-25° C.for 7 days. Similarly, it is expected that the nonwoven materials ofthis invention can be sterilized by exposure to electron beamirradiation. Alternatively, the materials of this invention can besterilized by gas or vapor phase antimicrobial agents such as ethyleneoxide, hydrogen peroxide plasma, peracetic acid, ozone, and similaralkylating and/or oxidizing agents.

The hydrophilic characteristic of the fibers may improve articles suchas wound and surgical dressings by improving absorbency. If the finefibers is used in a wound dressing backing film, the film may bepartially (e.g. zone or pattern) coated or completely coated withvarious adhesives, including but not limited to pressure sensitiveadhesives (PSAs), such as acrylic and block copolymer adhesives,hydrogel adhesives, hydrocolloid adhesives, and foamed adhesives. PSAscan have a relatively high moisture vapor transmission rate to allow formoisture evaporation. Suitable pressure sensitive adhesives includethose based on acrylates, polyurethanes, KRATON and other blockcopolymers, silicones, rubber based adhesives as well as combinations ofthese adhesives. The preferred PSAs are medical adhesives that areapplied to skin such as the acrylate copolymers described in U.S. Pat.No. RE 24,906, the disclosure of which is hereby incorporated byreference, particularly a 97:3 iso-octyl acrylate: acrylamide copolymer.Also preferred is an 70:15:15 iso-octyl acrylate-ethyleneoxideacrylate:acrylic acid terpolymer, as described in U.S. Pat. No.4,737,410 (Example 31), the disclosure of which is hereby incorporatedby reference. Other useful adhesives are described in U.S. Pat. Nos.3,389,827; 4,112,213; 4,310,509; and 4,323,557; the disclosures of whichare hereby incorporated by reference. Inclusion of medicaments orantimicrobial agents in the adhesive is also contemplated, as describedin U.S. Pat. Nos. 4,310,509 and 4,323,557.

Other medical devices that may be made, in whole or in part, of the finefibers include: surgical mesh, slings, orthopedic pins (including bonefilling augmentation material), adhesion barriers, stents, guided tissuerepair/regeneration devices, articular cartilage repair devices, nerveguides, tendon repair devices, atrial septal defect repair devices,pericardial patches, bulking and filling agents, vein valves, bonemarrow scaffolds, meniscus regeneration devices, ligament and tendongrafts, ocular cell implants, spinal fusion cages, skin substitutes,dural substitutes, bone graft substitutes, bone dowels, and hemostats.

An alternative melt blown process that may benefit from the use of thefibers, and the methods of making as provided herein, and useful inconsumer hygiene products, such as adult incontinence, infant diapers,feminine hygiene products, and others, is described in Applicants'co-pending application, U.S. Patent Application Publication No.2008/0160861,-0200890-A1, and incorporated by reference herein in itsentirety.

Articles comprising the dimensionally stable nonwoven fibrous webs ofthe present disclosure fine fibers may be made by processes known in theart for making products like polymer sheets from polymer resins. Formany applications, such articles can be placed in water at 23° C.without substantial loss of physical integrity (e.g. tensile strength)after being immersed 2 hours and dried. Typically, these articlescontain little or no water. The water content in the article afterextruding, injection molding or solvent casting is typically no greaterthan 10% by weight, preferably no greater than 5% by weight, morepreferably no greater than 1% by weight and most preferably no greaterthan 0.2% by weight.

Articles made of the dimensionally stable nonwoven fibrous webs of thepresent disclosure may be solvent, heat, or ultrasonically weldedtogether as well as being welded to other compatible articles. Thedimensionally stable nonwoven fibrous webs of the present disclosure maybe used in conjunction with other materials to form constructions suchas sheath/core materials, laminates, compound structures of two or morematerials, or useful as coatings on various medical devices. Thedimensionally stable nonwoven fibrous webs described herein may beparticularly useful in the fabrication of surgical sponges.

The hydrophilic characteristic of some exemplary dimensionally stablenonwoven fibrous webs of the present disclosure may improve articlessuch as wound and surgical dressings by improving absorbency. If thefine fibers is used in a wound dressing backing film, the film may bepartially (e.g. zone or pattern) coated or completely coated withvarious adhesives, including but not limited to pressure sensitiveadhesives (PSAs), such as acrylic and block copolymer adhesives,hydrogel adhesives, hydrocolloid adhesives, and foamed adhesives. PSAscan have a relatively high moisture vapor transmission rate to allow formoisture evaporation.

Suitable pressure sensitive adhesives include those based on acrylates,polyurethanes, KRATON and other block copolymers, silicones, rubberbased adhesives as well as combinations of these adhesives. Thepreferred PSAs are the normal adhesives that are applied to skin such asthe acrylate copolymers described in U.S. Pat. No. RE 24,906, thedisclosure of which is hereby incorporated by reference, particularly a97:3 iso-octyl acrylate:acrylamide copolymer. Also preferred is an70:15:15 iso-octyl acrylate-ethyleneoxide acrylate: acrylic acidterpolymer, as described in U.S. Pat. No. 4,737,410 (Example 31), thedisclosure of which is hereby incorporated by reference. Other usefuladhesives are described in U.S. Pat. Nos. 3,389,827; 4,112,213;4,310,509 and 4,323,557, the disclosures of which are herebyincorporated by reference. Inclusion of medicaments or antimicrobialagents in the adhesive is also contemplated, as described in U.S. Pat.Nos. 4,310,509 and 4,323,557.

Other medical devices that may be made, in whole or in part, ofexemplary dimensionally stable nonwoven fibrous webs of the presentdisclosure include: sutures, suture fasteners, surgical mesh, slings,orthopedic pins (including bone filling augmentation material), adhesionbarriers, stents, guided tissue repair/regeneration devices, articularcartilage repair devices, nerve guides, tendon repair devices, atrialseptal defect repair devices, pericardial patches, bulking and fillingagents, vein valves, bone marrow scaffolds, meniscus regenerationdevices, ligament and tendon grafts, ocular cell implants, spinal fusioncages, skin substitutes, dural substitutes, bone graft substitutes, bonedowels, and hemostats.

As part of the process for making the fine fibers, the aliphaticpolyester in a melt form is mixed in a sufficient amount relative to theviscosity modifier to yield fine fibers having average diametercharacteristics as described herein.

A variety of equipment and techniques are known in the art for meltprocessing polymeric fine fibers. Such equipment and techniques aredisclosed, for example, in U.S. Pat. No. 3,565,985 (Schrenk et al.);U.S. Pat. No. 5,427,842 (Bland et. al.); U.S. Pat. Nos. 5,589,122 and5,599,602 (Leonard); and U.S. Pat. No. 5,660,922 (Henidge et al.).Examples of melt processing equipment include, but are not limited to,extruders (single and twin screw), Banbury mixers, and Brabenderextruders for melt processing the inventive fine fibers.

The ingredients of the fine fibers may be mixed in and conveyed throughan extruder to yield a polymer, preferably without substantial polymerdegradation or uncontrolled side reactions in the melt. Potentialdegradation reactions include transesterification, hydrolysis, chainscission and radical chain define fibers, and process conditions shouldminimize such reactions. The processing temperature is sufficient to mixthe biodegradable aliphatic polyester viscosity modifier, and allowextruding the polymer.

The (BMF) meltblowing process is a method of forming a nonwoven fiberweb where a polymer fluid, either melt or solution, is extruded throughone or more rows of holes then impinged by a high velocity gas jet. Thegas jet, typically heated air, entrains and draws the polymer fluid andhelps to solidify the polymer into a fiber. The solid fiber is thencollected on solid or porous surface as a nonwoven web. This process isdescribed by Van Wente in “Superfine Thermoplastic Fibers”, IndustrialEngineering Chemistry, vol. 48, pp. 1342-1346. An improved version ofthe meltblowing process is described by Buntin et al. as described inU.S. Pat. No. 3,849,241, and incorporated by reference herein in itsentirety.

The viscosity modifiers described herein need not be added to the fiberextrusion process in a pure state. The viscosity modifiers may becompounded with the aliphatic polyester, or other materials prior toextrusion. Commonly, when additives such as viscosity modifiers arecompounded prior to extrusion, they are compounded at a higherconcentration than desired for the final fiber. This high concentrationcompound is referred to as a masterbatch. When a masterbatch is used,the masterbatch will generally be diluted with pure polymer prior toentering the fiber extrusion process. Multiple additives may be presentin a masterbatch, and multiple masterbatches may be used in the fiberextrusion process.

The dimensionally stable nonwoven fibrous webs of the present disclosuremay also be useful in consumer hygiene products, such as adultincontinence, infant diapers, feminine hygiene products, and others asdescribed in Applicants' co-pending application. An alternative meltblown process that may benefit from the use of viscosity modifiers asprovided herein is described in U.S. Patent Application Publication No.2008-0160861, filed Dec. 28, 2006, and incorporated by reference hereinin its entirety.

EXEMPLARY EMBODIMENTS

Embodiment 1 is a nonwoven web including a plurality of fiberscomprising:

one or more thermoplastic polyesters selected from aliphatic polyestersand aromatic polyesters; and

polypropylene in an amount greater than 0% and no more than 10% byweight of the web, and

one or more alkyl, alkenyl, aralkyl or alkaryl anionic surfactantsincorporated into the polyester;

wherein the web has at least one dimension in the plane of the web whichdecreases by no greater than 10% when the web is heated to a temperatureabove a glass transition temperature of the fibers in an unrestrainedcondition.

Embodiment 2 is the web of embodiment 1, wherein the one or more anionicsurfactant has a melting point of less than 200° C.

Embodiment 3 is the web of any of the preceding embodiments, wherein thenonwoven web remains hydrophilic after more than 10 days at 45° C.

Embodiment 4 is the web of any one of the preceding embodiments, furthercomprising a surfactant carrier.

Embodiment 5 is the web of any one of the preceding embodiments, whereinthe anionic surfactant is selected from the group consisting of one ormore alkyl, alkenyl, alkaryl and arakyl sulfonates; alkyl, alkenyl,alkaryl and arakyl sulfates; alkyl, alkenyl, alkaryl and arakylphosphonates; alkyl, alkenyl, alkaryl and arakyl phosphates; alkyl,alkenyl, alkaryl and arakyl carboxylates; alkyl alkoxylatedcarboxylates; alkyl alkoxylated sulfates; alkylalkoxylated sulfonates;alkyl alkoxylated phosphates; and combinations thereof.

Embodiment 6 is the web of any one of the preceding embodiments, whereinthe anionic surfactant is selected from the group consisting of (C₈-C₂₂)alkyl sulfate salts, di(C₈-C₁₈) sulfosuccinate salts, C₈-C₂₂ alkylsarconsinate salts, C₈-C₂₂ alkyl lactyalte salts, and combinationsthereof.

Embodiment 7 is the web of any one of the preceding embodiments, whereinthe anionic surfactant is present in an amount of at least 0.25% and nogreater than 8% by weight of the composition.

Embodiment 8 is the web of any one of the preceding embodiments, whereinthe anionic surfactant is present in an amount greater than 1% by weightof the composition.

Embodiment 9 is the web of any one of the preceding embodiments, whereinthe surfactant carrier is a liquid at 23° C.

Embodiment 10 is the web of any one of the previous embodiments, whereinthe surfactant carrier is selected from the group consisting ofpolyalkylene glycol, polyhydric alcohols, glycerin triglycerides, citricacid esters, aliphatic diesters and combinations thereof

Embodiment 11 is the web of any of the preceding embodiments, whereinthe anionic surfactant comprise less than 5% water.

Embodiment 12 is the web of any of the preceding embodiments, whereinthe surfactant carrier comprises less than 5% water.

Embodiment 13 is the web of any of the preceding claims, furthercomprising a plasticizer distinct from the anionic surfactant anddistinct from the surfactant carrier.

Embodiment 14 is the web of any one of the preceding embodiments,wherein the anionic surfactant is present in an amount greater than 2percent by weight of the aliphatic polyester.

Embodiment 15 is a nonwoven web including a plurality of fine fiberscomprising:

one or more thermoplastic polyesters selected from aliphatic polyestersand aromatic polyesters; and

polypropylene in an amount greater than 0% and no more than 10% byweight of the web, and

a viscosity modifier having the following structure:(R—CO₂ ⁻)_(n)M^(n+)

wherein R is an alkyl or alkylene of C8-C30 as a branched or straightcarbon chain, or C12-C30 aralkyl, and may be optionally substituted with0-100 alkylene oxide groups such as ethylene oxide, propylene oxidegroups, oligameric lactic and/or glycolic acid or a combination thereof;and

M is H, an alkali metal, an alkaline earth metal, or an ammonium group,a protonated tertiary amine or a quaternary amine;

n is 1 or 2 and is equal to the valence of the cation, and

wherein the web has at least one dimension in the plane of the web whichdecreases by no greater than 10% when the web is heated to a temperatureabove a glass transition temperature of the fibers but below the meltingtemperature when measured in an unrestrained condition.

Embodiment 16 is the web of embodiment 15, wherein the ammonium group isa protonated tertiary amine or a quaternary amine.

Embodiment 17 is the web of any one of embodiments 15-16, wherein M isan alkali metal or alkaline earth metal.

Embodiment 18 is the web of any one of embodiments 15-17, wherein theviscosity modifier is selected from the group consisting of selectedfrom the group consisting of alkyl carboxylates, alkenyl carboxylates,aralkyl carboxylates, alkylethoxylated carboxylates, aralkylethoxylatedcarboxylates, alkyl lactylates, alkenyl lactylates, stearoyl lactylates,stearates, the carboxylic acids thereof, and mixtures thereof.

Embodiment 19 is the web of any one of embodiments 15-18, wherein theviscosity modifier is present in an amount of no greater than about 10percent by weight of the web.

Embodiment 20 is the web any one of the preceding embodiments, furthercomprising a thermoplastic polymer distinct from the thermoplasticaliphatic polyester.

Embodiment 21 is the web of any one of the preceding embodiments,wherein the viscosity modifier is present in an amount less than 2% byweight.

Embodiment 22 is the web of any one of the preceding embodiments,wherein the viscosity modifier comprises less than 5% water.

Embodiment 23 is the web of any one of the preceding embodiments,wherein the molecular orientation of the fibers results in abi-refringence value of at least 0.01.

Embodiment 24 is the web of any of the preceding embodiments, whereinthe thermoplastic polyester is at least one aliphatic polyester selectedfrom the group consisting of one or more poly(lactic acid),poly(glycolic acid), poly(lactic-co-glycolic acid), polybutylenesuccinate, polyhydroxybutyrate, polyhydroxyvalerate, blends, andcopolymers thereof.

Embodiment 25 is the web of any of the preceding embodiments, whereinthe aliphatic polyester is semicrystalline.

Embodiment 26 is the web of any one of the preceding embodiments 1-20,further comprising a thermoplastic (co)polymer distinct from thethermoplastic polyester.

Embodiment 27 is the web of any of the preceding embodiments, whereinthe thermoplastic aliphatic polyester is present in an amount greaterthan 90% by weight of the thermoplastic polymer present in thecomposition.

Embodiment 28 is the web of any one of the preceding embodiments,wherein the polypropylene is present in an amount from about 1% to about6% by weight of the web.

Embodiment 29 is the web of any one of the preceding embodiments,wherein the fibers exhibit a median fiber diameter of no greater thanabout one micrometer (μm).

Embodiment 30 is the web of any one of the preceding embodiments,wherein the fibers exhibit a median fiber diameter of no greater thanabout 12 μm.

Embodiment 31 is the web of embodiment 30, wherein the fibers exhibit amedian fiber diameter of at least 1 μm.

Embodiment 32 is the web of any one of the preceding embodiments,wherein the web is biocompatible.

Embodiment 33 is the web of any one of the preceding embodiments,wherein the web is a nonwoven web formed from a molten mixturecomprising the thermoplastic polyester and the polypropylene.

Embodiment 34 is the web of any one of the preceding embodiments,wherein the nonwoven web is selected from the group consisting of aspunbond web, a blown microfiber web, a hydroentangled web, orcombinations thereof.

Embodiment 35 is an article comprising the web of any one of thepreceding embodiments, selected from the group consisting of a gasfiltration article, a liquid filtration article, a sound absorptionarticle, a thermal insulation article, a surface cleaning article, acellular growth support article, a drug delivery article, a personalhygiene article, a dental hygiene article, an adhesive coated tape, anda wound dressing article.

Embodiment 36 a surgical or medical drape comprising the web of any oneof the preceding embodiments 1 to 34.

Embodiment 37 a surgical or medical gown comprising the web of any ofthe preceding embodiments 1 to 34.

Embodiment 38 a sterilization wrap comprising the web of any of thepreceding embodiments 1 to 34.

Embodiment 39 is the sterilization wrap of embodiment 38, furthercomprising a repellent additive on or in the web.

Embodiment 40 is a wound contact material or adhesive coated tapecomprising the web of any of the preceding embodiments 1 to 34.

Embodiment 41 is a personal hygiene article such as a diaper or femininehygiene pad comprising the web of any of the preceding embodiments 1 to34.

Embodiment 42 is the web of any one of the preceding embodiments,further comprising an antimicrobial component.

Embodiment 43 is the web of embodiment 41, wherein the antimicrobialcomponent is present in an amount greater than 5 percent by weight ofthe aliphatic polyester.

Embodiment 44 is the web of any one of embodiments 42-43, wherein theantimicrobial component is selected from a fatty acid monoester, a fattyacid di-ester, an organic acid, a silver compound, a quaternary ammoniumcompound, a cationic (co)polymer, an iodine compound, or combinationsthereof.

Embodiment 45 is the web of any one of the preceding embodiments,wherein the plurality of fibers are bonded together in at least pointlocations.

Embodiment 46 is a method of making a web according to any one of thepreceding embodiments 1 to 34 comprising:

forming a mixture comprising:

-   -   one or more thermoplastic polyesters selected from aliphatic        polyesters and aromatic polyesters,    -   polypropylene in an amount greater than 0% and no more than 10%        by weight of the mixture, and    -   one or more alkyl, alkenyl, aralkyl or alkaryl anionic        surfactants incorporated into the polyester;

simultaneously forming a plurality of fibers from the mixture; and

collecting at least a portion of the fibers to form a web, wherein theweb has at least one dimension which decreases by no greater than 10% inthe plane of the web when the web is heated to a temperature above aglass transition temperature of the fibers but below the meltingtemperature when measured in an unrestrained condition.

Embodiment 47 is the method of embodiment 46, further comprising asurfactant carrier.

Embodiment 48 is the method of any one of embodiments 46 or 47, furthercomprising the step or extruding the polyester blended with the anionicsurfactants.

Embodiment 49 is the method of any one of embodiments 46-48, wherein theblending of the polyester and the anionic surfactants comprisesextruding the polyester and the anionic surfactants.

Embodiment 50 is the method of any one of embodiments 46-49, furthercomprising the subsequent step of adding additional polyester.

Embodiment 51 is the method of any one of embodiments 46-50, furthercomprising post heating the extruded web.

Embodiment 52 is a method of making a web according to any one of thepreceding embodiments 1 to 34 comprising:

forming a mixture comprising:

-   -   one or more thermoplastic polyesters selected from aliphatic        polyesters and aromatic polyesters,    -   polypropylene in an amount greater than 0% and no more than 10%        by weight of the mixture; and    -   a viscosity modifier selected from the group consisting of alkyl        carboxylates, alkenyl carboxylates, aralkyl carboxylates,        alkylethoxylated carboxylates, aralkylethoxylated carboxylates,        alkyl lactylates, alkenyl lactylates, and mixtures thereof

simulataneously forming a plurality of fibers from the mixture; and

collecting at least a portion of the fibers to form a web, wherein theweb has at least one dimension which decreases by no greater than 10% inthe plane of the web when the web is heated to a temperature above aglass transition temperature of the fibers but below the meltingtemperature when measured in an unrestrained condition.

Embodiment 53 is the method of embodiment 52, wherein the web is formedusing a melt-blowing, spun-bonding, or melt-spinning process.

Embodiment 54 is the method of any one of embodiments 52-53, wherein thethermoplastic polyester and the viscosity modifier are mixed prior tothe web forming process.

Embodiment 55 is the method of any one of embodiments 52-54, furthercomprising the step of extruding the polyester blended with theviscosity modifier.

Embodiment 56 is the method of any one of embodiments 52-55, wherein themixing of the polyester and the viscosity modifier comprises extrudingthe polyester and the viscosity modifier.

Embodiment 57 is the method of any of the preceding embodiment 52-56,further comprising post heating the web.

Embodiment 58 is the method of any of the preceding embodiments 52-57,wherein the web is formed using melt-spinning, filament extrusion,electrospinning, gas jet fibrillation or combinations thereof.

Embodiment 59 is a method of making a web according to any one of thepreceding embodiments 46-58, wherein the fibers do not exhibit molecularorientation.

Test Methods

Apparent Surface Energy

The method for measuring the surface energy is AATCC Test Method118-1983, with the modifications described below. Surface energiesmeasured according to this modified test method are hereinafter referredto as “apparent” surface energies. AATCC test method 118-1983 determinesthe surface energy of a fabric by evaluating the fabric's resistance towetting by a series of selected hydrocarbon compositions. Thehydrocarbons set forth in AATCC 118-1983, however, only provide formeasurements of surface energy from about 19.8 to 27.3 dynes percentimeter at 25° C. This range is extended by employing variousmixtures of methanol and water in the fabric resistance test. Thecompositions and their representative surface tensions are as follows:

Volume % Surface Tension Liquid No. Methanol/Water (Dynes/cm at 20° C. 765/45 30 8 53/47 35 9 40/60 40 10 25/75 45 11 21/79 50 12 15/85 55 13 8.5/91.5 60

The test procedure is as follows. A specimen of the covering material isplaced flat on a smooth, horizontal surface. Using the method of AATCC118-1983 except that beginning with the lowest number test liquid, 5drops of the liquid are placed on the surface of the fabric on the sidewhich will face the resin impregnated sheet in various locations. Ifthree of the five drops wick into the fabric within 60 seconds, theliquid of the next higher surface tension is used. When at least 3 dropsremain on the fabric surface, the apparent surface energy is recorded asthe range of the last two liquids.

Effective Fiber Diameter

Fiber diameter is measured using the Effective Fiber Diameter (EFD)method developed by Davies using basis weight, web thickness, andpressure drop to estimate the average fiber diameter of a fiber web.Davies, C. N., The Separation of Airborne Dust and Particles, Inst. ofMech. Engineers, London, Proceedings 1B, 1952.

Average fiber diameter can be measured in several ways includingmicroscopy, laser diffraction, and fluid flow resistance. Davies(Davies, C. N., The Separation of Dust and Particles, Inst. of Mech.Engineers, London, Proceedings 1B, 1952) developed a correlation fordetermining the average diameter of a fiber web using the air flowresistance, web thickness, and web basis weight. Air flow resistance wasmeasured by recording the pressure drop of a 11.4 centimeter diameterweb sample at an air flow rate of 32 liters per minute. Web thicknesswas measured on a 13.3 centimeter diameter circular web sample with anapplied pressure of 150 Pa. Web basis weight was measured by weighing a13.3 centimeter diameter web sample. The equations described by Davieswere then used to determine the effective fiber diameter (EFD) of theweb, expressed in units of microns (1 micron=10E-6 meters).

Shrinkage

After extrusion, the fine fiber webs were also measured for shrinkage byplacing 10 cm×10 cm squares of the web on aluminum trays in an oven at80° C. for approximately 14 hours. After aging the squares were measuredand the average linear shrinkage was recorded.

EXAMPLES

The invention will be further clarified by the following examples whichare exemplary and not intended to limit the scope of the invention.

Glossary Of Terms

-   PLA 6202D Polylactic acid (Natureworks, Minnetonka, Minn.)-   PLA 4032 Polylactic acid (Natureworks, Minnetonka, Minn.)-   PLA 4060D Polylactic acid (Natureworks, Minnetonka, Minn.)-   PLA 6251D Polylactic acid (Natureworks, Minnetonka, Minn.)-   Brij 700 Steareth-100 (Sigma Aldrich, Milwaukee, Wis.)-   Pationic 138C Sodium lauroyl lactylate (RITA Corporation, Crystal    Lake, Ill.)-   Carbowax 400 polyethylene glycol (PEG) 400 (Dow Chemical, Midland,    Mich.)-   PEG/DOSS 50% docusate sodium USP in PEG 400, (Cytec Industries, West    Patterson, N.J.)-   Hostapon STCI-85 Sodium cocoyl isethionate, 85%, (Clariant, Wayne    N.J.)-   Hostapur SAS-93G Sodium C14-C17 alkyl sec. sulfonate, (Clariant,    Wayne N.J.)-   Montanov 202 Arachidyl Alcohol (and) Behenyl Alcohol (and) Arachidyl    Glucoside (Seppic, Fairfield, N.J.)-   Citroflex A4 acetyl tributyl citrate (Morflex Inc., Greensboro,    N.C.)-   Crodaphos SG PPG-5 ceteth 10 phosphate (Croda, Inc., Parsipanny,    N.J.)-   Pationic CSL Calcium Stearoyl Lactylate (CSL) (RITA Corp. Crystal    Lake, Ill.)    The polymer resin used in the examples is 6251D PLA available as    pellets from Natureworks, LLC, Minnetonka, Minn. Natureworks reports    6215D PLA to have a relative viscosity of 2.50 and a d-isomer    content of 1.4%. Using GPC, the molecular weight of the resin was    found to be 94,700 daltons for Mw, and 42,800 daltons for Mn.

Examples C1-C3, 1, and 2

The compositions listed in Table 1 were extruded on an experimentalspunbond making line. The spunbond nonwovens were made using theequipment and processing techniques for spunbond nonwovens described inU.S. Pat. No. 6,916,752.

Non-woven spunbond PLA samples were made with different concentrationsof surfactants. A non-woven spunbond PLA sample without any surfactantwas also made. This was done for the purpose of evaluating and comparingthe different samples' wettability, aging stability, and generalmechanical properties.

The initial step was to pre-compound the wetting agents into higherconcentration masterbatches. This was done using a 25 mm Berstorff UTXtwin screw extruder, fitted with a standard pelletizing die. The strandswere run through a 12 foot water bath and into a pelletizing puller.

Four masterbatches were made: 1) 95% PLA 6202D and 5% PEG 400

-   -   2) 95% PLA 6202D and 5% PEG/DOSS    -   3) 90% PLA 6202D and 10% Brij 700    -   4) 90% PLA 6202D and 10% Pationic 138C        The PLA was fed using a K-tron Feeder. The other additives were        all fed using a grid melter and were fed into Zone 4. Feed rates        were as follows:

PLA Pationic 6202D PEG400 PEGDOSS Brij 700 138C Feed Rate Feed Rate FeedRate Feed Rate Feed Rate Batch (lbs/hr) (lbs/hr) (lbs/hr) (lbs/hr)(lbs/hr) 1 95 5 2 95 5 3 58.5 6.5 4 61.2 6.8The zone temperatures were as follows:

Screw Melt Speed Extrud. Extrud. Zone Die - Temp - Batch (RPM) Amp KWZone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 Zone 7 Zone 8 Zone 9 10 ° F. °F. 1 550 31.9 7 101.2 380 380 380 380 380 380 380 380 380 380 413 2 55025.3 5.5 100.5 380 380 380 380 380 380 380 380 380 380 398.73 3 400 23.13.7 98.5 380 380 380 380 380 380 380 380 380 380 403.15 4 400 18.2 2.998.5 380 380 380 380 380 380 380 380 380 380 387.43After the strands passed through the water bath and the pelletizer, theywere collected in 5 gallon pail liners, with holes in the bottom toallow any excess water to run off. The liners were placed in 5 gallonpails and were raised from the bottom about 4 inches. Once the sampleshad been “drip dried”, the batches were distributed into multiple pansand allowed to crystallize in a batch oven at 65° C. for 12 to 24 hours.

The masterbatches and the virgin PLA were dried for a minimum of 6 hoursin a recirculated drier at 60° C. A web was made with 60 g/sq/m. Melttemperatures were about 190-210° C. When running Masterbatch 4 withPationic 138C, a dramatic viscosity reduction occurred, so thetemperature had to be dropped 160° C. The webs were passed through athrough air bonder on a screen support at a temperature of 90-100° C. inorder lightly bond the web.

Spunbond nonwoven examples were prepared using the masterbatchesdescribed above blended with neat 6202D PLA. All the materials weredried prior to use. The spunbond nonwovens were obtained using aDavis-Standard BLUE RIBBON (DS-20®) extruder (Davis StandardCorporation, Pawcatuck, Conn.) using a 2.0 inch/50 mm single screwextruder to feed into through a pump to an extrusion head includingmultiple die orifices.

The die head had a total of 512 orifice holes with an aliphaticpolyester polymer melt throughput of 0.50 g/hole/min (33.83 lb/hr). Thedie had a transverse length of 7.875 inches (200 mm). The hole diameterwas 0.040 inch (0.889 mm) and L/D ratio of 6. The melt extrusiontemperature at the die of the neat PLA was set at 215° C., while themelt extrusion temperature of PLA with the surfactant additives wasdependent on the type and amount of additives. The temperature wasadjusted in order to make similar webs to the control (pure aliphaticpolyester, PLA). A representative description of the web forming andbonding process is exemplified by U.S. Patent Publication No. US2008/0038976 A1, and incorporated herein as reference in its entirety.

TABLE 1 Aged at 5 C. Aged at 45 C. Time (Days): 0 7 14 28 42 0 7 14 2842 Wet- Wet- Wet- Wet- Wet- Wet- Wet- Wet- Wet- Wet- Out Out Out Out OutOut Out Out Out Out Surface Surface Surface Surface Surface SurfaceSurface Surface Surface Surface Tension Tension Tension Tension TensionTension Tension Tension Tension Tension (dynes/ (dynes/ (dynes/ (dynes/(dynes/ (dynes/ (dynes/ (dynes/ (dynes/ (dynes/ Sample Composition cm)cm) cm) cm) cm) cm) cm) cm) cm) cm) C1 95% PLA 6202D; 5% PEG-400 36 3636 36 36 36 N/A N/A N/A N/A C2 100% PLA 6202D 36 36 36 36 36 36 36 36 3636 C3 95% PLA 6202D; 5% Brij 700 36 36 36 36 36 36 42 45 45 45 1 95% PLA6202D; 5% DOSS/PEG 72 72 72 72 72 72 72 72 72 72 2 95% PLA 6202D; 5%Pationic 138C 72 72 72 72 72 72 72 72 72 72

The results indicate that virgin PLA (Comparative Example 2) ishydrophobic with an apparent surface energy of 36 dyne/cm throughout theaging at room temperature (23-25° C.) and ambient humidity. Addition ofPEG 400 (MP<23° C.) or the surfactant Brij 700 (MP=51-54° C.) did notimprove the hydrophilicity (Comparative Examples 1 and 3 respectively).Addition of the anionic surfactants docusate sodium (DOSS, MP=153-157°C.) and lauroyl lactylate (Pationic 138C, MP=50-55° C.) (Examples 1 and2) resulted in a dramatic improvement in the hydrophilicity which wasstable over time. The DOSS used was dissolved in a PEG 400 carrier (50%PEG400/50% DOSS solution, MP<23° C.) and formed a transparent solutionwhich simplified processing and may have contributed to the superiorhydrophilicity.

Examples C4-05 and 3-5

Samples were prepared with PLA 4032 using a Brabender Hot Melt MixerModel No. DR-2051. The Brabender was set to 200° C. and allowed to cometo temperature. The paddle speed was set to 0.70. PLA 4032 waspreweighed on a balance and added to the Brabender. Total mass offinished mixture was 60 g. PLA 4032 was mixed in the Brabender until auniform, molten mixture was made while the specified mass of additivesgradually added. Mixing times were typically 10-20 min. The Braebenderchamber was purged using Unipurge purge resin (Dow Chemical, Midland,Mich.), after every run.

The molten mixtures were pulled from the Brabender and pressed intouniform sheets using a hydraulic press. Samples were pressed at 195° C.and with 20,000 lbs of pressure for 60 seconds between two liners. Theliner was a silicone coated kraft paper release liner. Films were 50-125micron thick.

Formulations of PLA 4032 with various surfactants are shown below inTable 2 along with the contact angle measurements.

TABLE 2 Initial Contact Angle Measurements After 24 hrs at 72 C. Avg.Avg. Example Surfactant % Surf 1 2 3 Angle 1 2 3 Angle Avg. Change C4None 0 60 68 66 64.66667 84 70 78 77.33333 12.66667 C5 Montanov 202 5 8279 86 82.33333 58 66 46 56.66667 −25.66667 3 Pationic 138C 5 10 10 10 1010 10 10 10 0 4 Hostapon STCI 85G 5 58 52 54 54.66667 34 46 30 36.66667−18 5 Hostapur SAS-93G 5 10 10 10 10 30 28 30 29.33333 19.33333The virgin PLA was relatively hydrophobic. Addition of Montanov 202 didnot result in a hydrophilic film. Even after heating, the contact anglewas still greater than 50° C. The Pationic (alkyl carboxylate) resultedin a very hydrophilic film and heating to 72° C. did not alter theresult. The two sulfonate surfactants behaved differently. Theisethionate surfactant produced a film which was initially relativelyhydrophobic but after heating the contact angle decreased to 37 degrees.The C14-C17 alkyl sulfonate (Hostapur SAS) produced a hydrophilic film,however, aging for 24 hrs at 72° C. increased the contact angle to 29degrees. The inventive compositions resisted fogging when breathed on.

Examples 6-8

The following samples were made and tested according to the proceduredescribed in Examples C4-05 and Examples 3-5 above.

TABLE 3 Contact Angle Angle Example Number Component 6 7 8 NatureworksPLA 75 70 75 4060D Citroflex A4 20 20 20 Crodafos SG 5 10 2.5Triethanolamine 0 0 2.5 Total 100 100 100 Contact angle 30 23 22 Contactangle 28 18 22 Contact angle 22 26 20 Average Contact angle 26.7 22.321.3

These results show that the alkoxylated phosphate surfactant, CrodaphosSG, improved the hydrophilicity significantly. In comparison, thecontact angle of PLA with Citroflex plasticizer and no surfactant isstill very hydrophobic, having a contact angle in excess of 60 degrees(data not shown). The addition of Crodaphos SG in the acid form (Example6) reduced the contact angle to less than 27. Addition of more CrodaphosSG (Example 7) reduced the contact angle further and neutralization withtriethanolamine to make the phosphate salt reduced the contact anglefurther yet (Example 8).

Examples 9, 10

CSL was added to the system in the concentrations shown in Table 4 bydry blending the CSL powder with warm PLA pellets from the polymerdryer. The resin was predried by heating to 71 C overnight. The CSLmelted on contact with the warm PLA pellets and was blended by hand toform slightly sticky pellets that were then fed to the extruder.

For examples 9 and 10 and the control, die temperature was held at 225°C. and all other process conditions were held constant. The pump exitpressure measured the entire pressure drop of the polymer stream throughthe die and the necktube.

Example 10 with 2.0% CSL produced a small amount of polymer particlesalong with the fibers. This phenomenon is referred to as “sand”, and isa common flaw in BMF processing.

It was found that adding the CSL to neat PLA resin before or duringextrusion greatly reduced the pressure drop across the die as shown inTable 4. It was also noted that the fiber diameter decreasedsignificantly as well. After aging the squares were measured and theaverage linear shrinkage is also reported in Table 4.

TABLE 4 Pump Exit Eff. Fiber 80° C. Pressure Diameter Shrinkage ExampleMaterial (psi) (microns) (linear %) Control Neat 6251D PLA 671 19.614.25 9 1.0% CSL in 6251D 372 11.4 24.70 10 2.0% CSL in 6251D 262 9.710.08The finer diameter webs are noticeably softer and more conformablecompared to the control sample. The shrinkage of the webs that includedCSL was substantial.

Examples 11-13

CSL was pre-blended at high concentration prior to fiber formation. Thishigh concentration mixture is commonly called a masterbatch. Themasterbatch is typically dry blended with neat polymer pellets whenfeeding to the fiber extruder. The extrusion process then providesadditional mixing.

A masterbatch of 10% CSL in 6251D PLA was prepared on a twin screwextruder, cooled as strands in a water bath, then pelletized using a drypelletizer. The solid pellets were dried in an 80° C. oven overnight toremove any trace water from the water bath.

Melt-blown fibers were extruded using the same equipment as Example 9.Again extrusion temperature was held at 225° C. Four CSL samples wereproduced with final concentrations of CSL and the results shown in Table5.

TABLE 5 Pump Exit Eff. Fiber 80° C. Pressure Diameter Shrinkage ExampleMaterial (psi) (microns) (linear %) Control Neat 6251D PLA 431 16.8 3.1611 0.5% CSL in 6251D 142 11.7 13.91 12 0.75% CSL in 6251D 122 11.1 8.5013 1.0% CSL in 6251D 62 8.8 17.50

The 0.75% and 1.0% samples exhibited some sand in the finished webs.

The pump exit back pressure dropped precipitously with minor additionsof calcium stearoyl lactylate (Pationic CSL), as shown in FIG. 1. Aregression analysis of the data shows that the data fits the followingsecond order polynomial Melt viscosity=351(Pationic concentration)²−706(Pationic concentration)+428 where r²=0.985. Where Pationicconcentration is in weight % and melt viscosity is expressed as the pumpexit pressure in PSI (lbs/in²).”

The polynomial shows that the viscosity modifier dramatically effectsmelt viscosity.

Examples 14-19

Other fatty salts have shown to be effective in reducing fiber diameteralong with CSL. For these experiments, various powdered salts in theconcentrations shown in Table 3 were dry blended with neat PLA pelletsprior to extrusion. The additives tested included:

Sodium Stearoyl Lactylate (SSL) (PATIONIC SSL, from RITA Corp.)—as anoff-white powder

Calcium Stearate (Ca—S) (Aldrich, St. Louis, Mo.)

Sodium Behenoyl Lactylate (SBL) (PATIONIC SBL, from RITA Corp.) as anoff-white colored powder

Examples 14-19 were run on slightly larger equipment such that pressuremeasurements were not directly comparable between the two pieces ofequipment. The operating temperature was held constant at 210° C. Theresults of the experiment are shown in Table 6. During the extrusion runthe pump exit pressure sensor failed, and no reading was taken for thecontrol sample.

All three of these salts (SSL, SBL, Ca—S) produced webs that containedlarger amounts of sand than CSL, which gave the webs a very rough feel.However despite the sand, both additives substantially reduced the fiberdiameter of the melt-blown webs.

TABLE 6 Pump Exit Eff. Fiber 80° C. Pressure Diameter Shrinkage ExampleMaterial (psi) (microns) (linear %) Control Neat 6251D PLA Failed sensor25.8 6.0 14 1% SSL in 6251D 744 16.7 17.75 15 1.5% SSL in 6251D 968 15.59.75 16 2% SSL in 6251D 425 12.7 29.0 17 2% SBL in 6251D 69 5.5 19.25 181% Ca—S in 6251D 83 10.0 10.25 19 2% Ca—S in 6251D 44 8.0 23.08

Example 20 Spunbond PLA with Polypropylene

Nonwoven webs were made using the spunbond process from neat poly(lacticacid) (PLA) and a mixture of PLA and polypropylene (PP). The PLA usedwas grade 6202D from Natureworks, LLC (Minnetonka, Minn.). The PP usedwas grade 3860X from Total Petrochemicals (Houston, Tex.). One samplealso contained a 50/50 mixture Dioctyl sulfosuccinate sodium salt (DOSS)and poly(ethylene glycol) (PEG) as a plasticizer, diluent, andhydrophilic surfactant. The DOSS/PEG mixture was compounded with 6202DPLA and added as a master batch to the spunbond process.

The spunbond apparatus used is that described in U.S. Pat. No. 6,196,752(Berrigan et al.). The extruder used was a 2 inch (5 cm) single screwextruder from Davis-Standard (Pawcatuck, Conn.). The die used had aneffective width of 7.875 inches (20.0 cm) and was fed polymer melt froma metering pump at the rate of 42 pounds (19.1 kg) per hour. The die had648 holes, each hole being 0.040 inches (10.2 mm) in diameter with a L/Dof 6. The extrusion temperature was 230° C. The air attenuator was setat a pressure of 5 pounds per square inch (34.5 kilopascal). Processconditions were kept constant for the different mixtures. Spinning speedis the filament speed calculated using the final average fiber diameter,measured microscopically, and the polymer rate per hole. In all casesthe spinning speed is no greater than 2500 meters per minute, the speedat which strain induced crystallization begins in PLA.

After extrusion the webs were also measured for shrinkage by placing anunrestrained 10 cm×10 cm square section cut from the middle of each webusing a die cutter onto an aluminum tray in a convection oven at 80° C.overnight (e.g. for approximately 14 hours). The Tg of the PLA webs wasapproximately 54-56° C. The heated samples were then allowed to cool andmeasured for length (in the machine direction) and width (in the crossdirection), and the average linear shrinkage of three samples wasreported. The shrinkage reported was the average change of three samplesin sample length and width, as opposed to change in sample area. Thusfor each reported composition a total of three lengths and three widthswere averaged. It was found that there no significant difference inlength and width shrinkage.

TABLE 7 Results for Example 20 Fiber Spinning 80° C. Diameter SpeedShrinkage Material (micrometers) (m/min) (linear %) Neat 6202D PLA 152121 5.56 6202D + 3% PP 17 1651 2.84 6202D + 3% 18 1473 7.61 DOSS/PEG +3% PP

Example 21 Meltblown PLA with Polypropylene

Nonwoven webs were produced using a meltblowing process from poly(lacticacid), PLA, and polypropylene, PP. The PLA used was grade 6251D fromNatureworks, LLC, (Minnetonka, Minn.). The PP used was grade 3960 fromTotal Petrochemicals (Houston, Tex.).

The meltblowing apparatus consisted of a twin screw extruder, andmetering pump and a meltblowing die. The extruder used was a 31 mmconical twin screw extruder (C.W. Brabender Instruments (SouthHackensack, N.J.). After the extruder a positive displacement gear pumpwas used to meter and pressurize the polymer melt. The metered melt wassent to a drilled orifice meltblowing die. Drilled orifice meltblowingdies are described in U.S. Pat. No. 3,825,380. The die used was 10inches (25.4 cm) wide with 20 polymer orifices per inch (per 2.54 cm) ofwidth, each orifice being 0.015 inches (381 micrometers) in diameter.The die was operated at a temperature of 225° C. Different mixtures ofpolymer pellets were fed to the process with amounts of PP added to thePLA. Process conditions were kept constant throughout the experiment.

The webs were collected on a vacuum collector and wound up onto coresusing a surface winder. Fiber diameter was measured using the airflowresistance technique described by Davies (Davies, C. N., The Separationof Airborne Dust and Particles, Inst. of Mech. Engineers, London,Proceedings 1B, 1952), this measurement is referred to as EffectiveFiber Diameter or EFD. Shrinkage was measured using the techniquedescribed in Example 20. Some samples expanded during heating, and thesesamples are reported as having negative shrinkage values.

TABLE 8 Example 21 Results Eff. Fiber 80° C. Diameter Shrinkage Material(micrometers) (linear %) Neat 6251D PLA 15.7 12.25 1% 3960 PP in 6251D15.8 2.08 2% 3960 PP in 6251D 15.8 1.83 4% 3960 PP in 6251D 16.4 −0.088% 3960 PP in 6251D 15.7 −1.50

Example 22 Meltblown PLA with Viscosity Modifying Salts

Nonwoven webs were produced using the meltblowing process using PLA anda number of salts that greatly reduce the apparent viscosity of the meltduring processing. The fiber diameters of the finished nonwoven webswere also smaller when the salts are added. Polypropylene was also addedto some mixtures to reduce the shrinkage of the nonwoven webs. Theresulting web had the properties of both reduced fiber diameter andreduced shrinkage. The polypropylene used was grade 3960 from TotalPetrochemicals (Houston, Tex.). The PLA used was grade 6251D fromNatureworks, LLC (Minnetonka, Minn.). The additives tested included:

Calcium Stearoyl Lactylate (CSL) (Trade name Pationic CSL, fom RITACorp. (Crystal Lake, Ill.);

Sodium Stearoyl Lactylate (SSL) (trade name Pationic SSL from RITA Corp.(Crystal Lake, Ill.);

Calcium Stearate (Ca—S) from Aldrich (St. Louis, Mo.);

Sodium Behenoyl Lactylate (SBL) (trade name Pationic SBL) from RITA Corp(Crystal Lake, Ill.).

The meltblowing process is the same as that used in Example 2. Theprocess was operated with a die temperature of 225° C. The salts wereadded to the system by dry blending the powder with warm PLA pelletsfrom the polymer dryer. The resin was predried by heating to 71° C.overnight. The salt additive melted on contact with the warm PLA pelletsand was blended by hand to form slightly sticky pellets that were thenfed to the extruder.

After extrusion the webs were tested for EFD and thermal shrinkage usingthe same methods as in previous examples. The pressure of the polymerentering the die was recorded as a surrogate for polymer viscosity. Inthis manner any decrease in apparent viscosity of the melt is seen as adecrease in pressure at the die entrance.

TABLE 9 Example 22 Results Die Entrance Eff. Fiber 80° C. PressureDiameter Shrinkage Material (psi) (micrometers) (linear %) Neat 6251DPLA 431 16.8 13.16 0.5% CSL in 6251D 142 11.7 13.91 0.75% CSL in 6251D122 11.1 8.50 1.0% CSL in 6251D 62 8.8 17.50 2% SSL in 6251D 425 12.729.0 2% SBL in 6251D 69 5.5 19.25 1% Ca—S in 6251D 83 10.0 10.25 2% Ca—Sin 6251D 44 8.0 23.08 0.5% CSL, 4% PP in 6251D 401 13.5 −3.47 1% CSL, 4%PP in 6251D 323 11.4 −1.62 1.5% CSL, 4% PP in 6251D 387 11.3 −0.67 1.0%CSL, 2% PP in 6251D 415 10.4 −3.47 1.0% CSL, 6% PP in 6251D 292 11.0−1.93

Example 23 Meltblown PET with Polypropylene

Fiber webs of were made using the meltblowing process with blends of PPin PET. The PET resin used was grade 8603A from Invista (Wichita,Kans.). The polypropylene used was grade 3868 from Total Petrochemicals(Houston, Tex.).

The meltblowing apparatus used consisted of a single screw extruder, andmetering pump, and a meltblowing die. The extruder used was a 2 inch(5.1 cm) single screw extruder (David Standard, Pawcatuck, Conn.). Afterthe extruder a positive displacement gear pump was used to meter andpressurize the polymer melt. The metered melt was sent to a drilledorifice meltblowing die. Drilled orifice meltblowing dies are describedin U.S. Pat. No. 3,825,380. The die used was 20 inches (50.8 cm) widewith 25 polymer orifices per inch of width, each orifice being 0.015inches (381 micrometers) in diameter. Blending was accomplished byfeeding a dry-blended mixture of the PET and PP pellets to the extruder.Process conditions were kept constant for the different mixtures.

After the nonwoven webs were formed, they were tested for shrinkage inthe same manner as the previous PLA samples. However due to the higherglass transition of PET the convection oven was set to 150° C., ratherthan the previous 80° C.

TABLE 10 Example 23 Results 150° C. Shrinkage Material (Linear %) Neat8603F 30.08 8603F + 3% PP 7.17 8603F + 5% PP 4.17 8603F + 10% PP 2.00

Example 24 Meltblown PLA with Additional polymeric Additives

Additional samples were melt blended with PLA and extruded as meltblownfibers using the same equipment as described in Example 21 with thefollowing parameters. The die used was 10 inches (25.4 cm) wide with 25polymer orifices per inch (per 2.54 cm) of width, each orifice being0.015 inches (381 micrometers) in diameter; the die was operated at atemperature of 225° C.; the air heater temperature was 275° C.; the airpressure was 9.8 psi (67.6 kilopascal); the collector distance was 6.75inches (17.1 cm) and the collector speed was 2.3 ft/min (0.70meters/min). The air gap was 0.030 inches and air knife set back was0.010 inches (254 micrometers). Air gap is the thickness of the airslots formed by the gaps between the air knives and die tip. The airknife set back is defined as the distance that the face of the airknives are set behind the apex of the die tip. (i.e. a positive set backimplies the apex of the die tip extends beyond the face of the airknives) Nonwoven webs were produced using a meltblowing process frompoly(lactic acid). The PLA used was grade 6251D from Natureworks, LLC,(Minnetonka, Minn.). The polymer additives are shown in Table 11 below.

TABLE 11 Additives in PLA Additive Level Additive Manufacturer Wt %Control — 0 Polypropylene (PP) Total Total Petrochemicals, 11.7 3860,100 MFI Houston, TX PP, Total 3505G, 400 MFI Total Petrochemicals, 5Houston, TX PP, Total 3762, 18 MFI Total Petrochemicals, 5 Houston, TXKraton FG1901 Kraton Polymers, 5 Houston, TX Kraton D1117P (SIS) KratonPolymers 5 Houston, TX LDPE, Marflex 4517 Chevron-Phillips 5 Chemical,The Woodlands, TX LLDPE Dowlex 2035 Dow Chemical, Midland 5 MI LLDPEDowlex 2035 Dow Chemical, Midland 2 MI Lotryl 37EH175, 2EHA/MA ArkemaInc USA, 5 copolymer Philadelphia, PA Polycaprolactone, MW SigmaAldrich, 5 70-90,000 Milwaukee, WI Polyethylene oxide, MW Sigma Aldrich,5 200,000 Milwaukee, WI HDPE, HD 7845.30 ExxonMobil Chemical, 5 Houston,TX Depart W40-5, Monosol, Merrillville, IN 5 polyvinylalcohol Note: MFIfor the polypropylenes has the units of grams per 10 min.

The effective fiber diameter (EFD) was measured by the same techniquedescribed in Example 21. The basis weight was measured by weighing a 10cm×10 cm die cut sample and calculating to a meter base. The % shrinkagewas measured as described in Example 20 using 10×10 centimeter samples.Three samples were measured. The shrinkage reported was the averagechange of three samples in sample length and width, as opposed to changein sample area. The results are shown in Table 12 below.

TABLE 12 Additives in PLA- Physical Property Results Basis 80° C. wt EFDShrinkage Additive Comments on web g/M² microns (linear %) Control — 7813.2 26.7 Polypropylene (PP) — 74 12.9 −1.7 Total 3860, 100 MFI PP,Total 3505G, — 73 13.2 −2.3 400 MFI PP, Total 3762, — 74 13.2 −0.3 18MFI Kraton FG1901 No sample obtained, — — — poor fiber formation KratonD1117P — 72 13.9 19.3 (SIS) LDPE, Marflex 4517 No sample obtained, — — —poor fiber formation LLDPE Dowlex 2035 No sample obtained, — — — poorfiber formation LLDPE Dowlex 2035 — 71 23.2 3.7 Lotryl 37EH175, — 7614.1 21 2EHA/MA copolymer Polycaprolactone, — 74 23.2 4.3 MW 70-90,000Polyethylene oxide, — 73 17.3 3.3 MW 200,000 HDPE, HD 7845.30 No sampleobtained, poor fiber formation Depart W40-5, No sample obtained, 76 11.618.7 polyvinylalcohol poor fiber formation Note: MFI (melt flow index)for the polypropylenes has the units of grams per 10 min.

Thus, low or no shrinkage fibers were obtained from polypropylene over abroad molecular weight as indicated by the broad melt index polymersused. Low shrinkage fibers were also obtained using polycaprolactone, ahigh molecular weight polyethylene oxide, and linear low densitypolyethylene (when used at a lower concentration). For the most part,the results shown here are only for polymer additives at a singleconcentration (5%). Each polymer type may have a unique optimumconcentration to optimize web fiber formation, feel, shrinkage andphysical properties such as tensile and elongation.

FIGS. 2-3 show the dispersed polypropylene as described herein. All arefrom samples in Table VI. All are at 2000X and done by embedding thesample followed by microtoming, staining to enhance constrast andimaging by Transmission Electron Microscopy (TEM). FIG. 2 is PLA alone(Control in Table IV); and FIG. 3 is PLA with 5% by weight Total 3860PP.

Example 25

Exemplary embodiments of spunbond nonwovens made of PLA polymer blendsto enhance compaction are disclosed in the following examples: Example25 illustrates the interactions of the various blends without additives;Example 26 illustrates the interactions of the various blends inpresence of additives; and finally Example 27 demonstrates the efficacyof using the PLA polymer blends for making spunbond webs at a pilotplant operating at typical production conditions.

Spunbond nonwoven webs were made from various blends of poly(lacticacid) (PLA). The PLA grades used were 6202D, 6751D, and 6302D fromNatureworks, LLC (Minnetonka, Minn.). Characteristics of the PLA gradesare shown in Table 13. All the PLA materials were dried before use.

TABLE 13 PLA Grade Mw Mn PDI D-content (%) 6302 1.33 × 10⁵ 7.44 × 10⁴1.78 9.85 6751 1.47 × 10⁵ 7.59 × 10⁴ 1.94 4.15 6202 1.34 × 10⁵ 8.37 ×10⁴ 1.60 2.0 PDI = polydispersity index “D-content” = % of the D isomerpresent in the PLA derived from a mixture of L and D lactic acidresidues.

Molecular weights of the PLA grades were determined using Size ExclusionChromatography. The value of the D-contents was provided by NatureWorks,Minnetonka, Minn.

The spunbond apparatus used is that described in U.S. Pat. No. 6,196,752(Berrigan et al.). The extruder used was a 2 inch (5 cm) single screwextruder from Davis-Standard (Pawcatuck, Conn.). The die used had aneffective width of 7.875 inches (20.0 cm) and was fed polymer melt froma metering pump at the rate of 45 pounds (20.4 kg) per hour (0.52g/hole/min). The die had 648 holes, each hole being 0.040 inches (1.02mm) in diameter with a L/D of 6. The extrusion temperature was 240° C.The spinning speed is the filament speed calculated using the finalaverage fiber diameter measure microscopically, and using the polymerrate per hole. The fiber webs after laydown were slightly bonded usingthrough-air-bonder (TAB) operating at 120° C.-125° C., then feed into acalendar with two smooth rolls with both top and bottom rolls at 80°C.-82° C.; and line speed of 85 fpm (26 m/min) and nip pressure of 150PLI (PLI=lbf/linear inch) (263 N/cm).

The tensile properties of the calendared webs were determined using theASTM D5035 test method. The fiber samples were obtained at laydownbefore the TAB and their sizes measure using an opticalmicroscope—Olympus DP71 Microscope with a digital camera. The percentcrystallinity of the webs were determined using TA Instruments Q2000(#131, Cell RC-00858) Modulated® Differential Scanning calorimeter(MDSC). A linear heating rate of 4° C./min. was applied with aperturbation amplitude of ±0.636° C. every 60 seconds. The specimenswere subjected to a heat-cool-heat profile over a temperature range of−25 to 210° C. Table 14 and Table 15 are summary of the fiber and webmechanical and thermal characteristics, and also process spinningspeeds. The thermal shrinkage of the webs was measured by placing a 10cm×10 cm sample in an air oven for 1 hour at 70° C. and 100° C. Allsamples exhibited less than 4% shrinkage.

TABLE 14 Fiber and Web (CD) characteristics Basis Spinning Max.Normalized Tensile % Wt Fiber Speed Load Load Strain CrystallinityComposition (gsm) Size (μ) (m/min) (N) (mN * sqM/g) (%) (MSDC) 95:56202/A 20 11.3 4450 2.00 100.0 36.11 32.6 92:8 6202/A 24 9.7 4496 2.3397.1 11.08 38.7 92:8 6202/B 24 12.4 3695 2.05 85.4 16.38 40.5 90:106202/B 24 11.7 4151 3.98 165.8 19.38 37.2 85:15 6202/B 24 10.3 4285 3.08128.3 17.31 22.6 80:20 6202/B 24 10.4 4203 4.22 175.8 19.11 34.4 A = PLA6302; B = PLA 6751

TABLE 15 Fiber and Web (MD) characteristics Basis Fiber Spinning Max.Normalized Tensile % Wt. Size Speed Load Load Strain CrystallinityComposition (gsm) (u) (m/min) (N) (mN * sqM/g) (%) (MDSC) 95:5 6202/A 2011.3 4450 15.2 757.5 36.2 32.6 92:8 6202/A 24 9.7 4496 10.4 432.1 12.938.7 92:8 6202/B 24 12.4 3695 11.0 459.2 20.2 40.5 90:10 6202/B 24 11.74151 14.9 620.0 17.9 37.2 85:15 6202/B 24 10.3 4285 9.1 378.3 20.0 22.680:20 6202/B 24 10.4 4203 18.8 782.1 17.5 34.4 A = PLA 6302, B = PLA6751

Example 26

Spunbond nonwoven webs were made from neat poly(lactic acid) (PLA)6202D, various blends of PLA, and a mixtures of PLAs with polypropylene(PP), and finally mixtures of PLAs with additives—50/50 mixture Dioctylsulfosuccinate sodium salt (DOSS) and poly(ethylene glycol) (PEG) andCitroflex A4. Masterbatches of the additives were compounding in PLA6202D. The PLA grades used were 6202D, 6751D, and 6302D fromNatureworks, LLC (Minnetonka, Minn.). Characteristics of the PLA gradesare shown in Table 13. All PLA materials including masterbatches weredried before use. The spunbond process conditions are similar as in withExample 25. The average spinning speeds were maintained at 4500m/min+/−200 m/min. The calendaring was done over two smooth rolls as inExample 25 and the operating conditions were as follows: Temperature oftop and bottom rolls was 77° C. (170 F), for 20-25 gsm webs the linespeed was 85-95 fpm (26-29 m/min), and nip pressures of 150 PLI (263N/cm); for 40 gsm (gram per square meter) webs the line speed wasaverage 60 fpm (18.3 m/min), and nip pressures of 300 PLI (526 N/cm).The thermal shrinkage of the webs was measured by placing a 10 cm×10 cmsample in an air oven for 1 hour at 70° C. All samples exhibited lessthan 5% shrinkage. The fiber sizes were obtained similar to methoddescribed in Example 25. A summary of the basis weight, melt extrusiontemperature, fiber size, and spinning speeds are shown in Table 16.

TABLE 16 Summary of some fabric characteristics and extrusion conditionsBasis Fiber Melt Spinning Wt. Size Temperature Speed Run Composition(gsm) (μ) (° C.) (m/min) 100% - 6202 20 9.81 240 4369 65:5 6202/6302 2210.1 240 4790 93:5:2 6202/6302/PP 20 11.2 240 4790 90:5:2:3 40 11.2 2404711 6202/6302/PP/PEGDOSS 92:8 6202/6302 30 10.3 240 4600 90:8:26202/6302/PP 25 10.4 240 4300 87:8:2:3 40 10.2 220 44786202/6302/PP/PEGDOSS 92:8 6202:6751 20 10.3 240 4390 90:8:2 6202/6751/PP20 10.1 240 4567 87:8:2:3 40 10.2 220 4478 6202/6751/PP/PEGDOSS 85:156202/6751 20 10.0 240 4659 83:15:2 6202/6751/PP 20 10.0 240 494380:15:2:3 40 10.4 220 4570 6202/6751/PP/PEGDOSS 80:20 6202/6751 20 10.2240 4751 78:20:2:3 6202/6751/PP 20 10.6 240 4400 75:20:2:3 40 10.4 2204570 6202/6751/PP/PEGDOSS 92:8 6202/Citroflex 20 10.4 220 4570 90:8:26202/Citroflex/PP 20 10.6 220 4400 87:8:2:3 40 10.7 220 4318Citroflex/PP/PEGDOSSSimilar to Example 25, the tensile properties of the calendared webswere determined using the ASTM D5035 test method. The tensile propertiesof the web in the cross direction are shown in Table 17. The tensileproperties of the web in the machine direction are shown in Table 18.

TABLE 17 Summary Normalized Tensile load in the Cross Direction Basis wtTensile Tensile/BW Run Composition (gsm) (N) mNM2/g 100% 6202D 20 1.9296.0 5% 6302D/2% PP 20 1.35 67.5 8% 6751D 20 2.59 129.5 8% 6751D/2% PP20 2.38 119.0 15% 6751D 20 2.97 148.5 15% 6751D/2% PP 20 2.62 131.0 20%6751D 20 3.33 166.5 20% 6751D/2% PP 20 2.88 144.0 8% Citroflex A-4 201.09 54.5 8% Citroflex A-4/2% PP 20 1.24 62.0 5% 6302D 22 1.48 67.3 8%6302D/2% PP 25 7.38 295.2 8% 6302D 30 2.93 97.7 5% 6302/2% PP/3% PEGDOSS40 2.79 69.8 8% 6302D/2% PP/3% PEGDOSS 40 3.64 91.0 8% 6751D/2% PP/3%PEGDOSS 40 2.78 69.5 15% 6751D/2% PP/3% PEGDOSS 40 2.65 66.3 20%67510/2% PP/3% PEGDOSS 40 3.01 75.3 8% A-4/2% PP/3% PEGDOSS 40 2.66 66.5

TABLE 18 Summary Normalized Tensile load in the Machine Direction Basiswt Tensile Tensile/BW Run Composition (gsm) (N) mNM2/g 100% 6202D 207.73 387 5% 6302D/2% PP 20 5.37 269 8% 6751D 20 9.35 468 8% 6751D/2% PP20 8.85 443 15% 6751D 20 9.52 476 15% 6751D/2% PP 20 10.99 550 20% 6751D20 7.93 397 20% 6751D/2% PP 20 8.39 420 8% Citroflex A-4 20 5.04 252 8%Citroflex A-4/2% PP 20 3.54 177 5% 6302D 22 7.70 350 8% 6302D/2% PP 252.74 110 8% 6302D 30 9.08 303 5% 6302/2% PP/3% PEGDOSS 40 8.58 215 8%6302D/2% PP/3% PEGDOSS 40 10.10 253 8% 6751D/2% PP/3% PEGDOSS 40 9.52238 15% 6751D/2% PP/3% PEGDOSS 40 9.82 246 20% 6751D/2% PP/3% PEGDOSS 4010.72 268 8% A-4/2% PP/3% PEGDOSS 40 8.48 212A summary of the normalized tensile load in both the CD and MD are shownas well in FIGS. 4 and 5 respectively. In order to account fordifferences in basis weight, the tensile load of each sample wasnormalized by dividing the maximum load by the basis weight andmultiplying by 1000.

The data shows that minor additions of additives such as Citroflex A4plasticizer and the PEG/DOSS hydrophilic surfactant/carrier cansignificantly reduce the tensile strength. The PLA blends had thehighest normalized tensile strength.

Example 27

Spunbond nonwoven webs were made from neat poly(lactic acid) (PLA)6202D, various blends of PLA, and a mixtures of PLAs with polypropylene(PP), and finally mixtures of PLAs with additives—50/50 mixture dioctylsulfosuccinate sodium salt (DOSS) and poly(ethylene glycol) (PEG) andCitroflex A4. Masterbatches of the additives were compounded in PLA6202D. The PLA grades used were 6202D, 6751D, and 6302D fromNatureworks, LLC (Minnetonka, Minn.). Characteristics of the PLA gradesare shown in Table 13. All PLA materials including masterbatches weredried before use. The spunbond were made on a 1 meter wide Reicofil 4line with a single beam with holes of about 5800 capillaries/meter withcapillary diameter of 0.6 mm. The process air temperatures in the upperand lower quench chambers were 70° and 50° C. respectively. Also thehumidity in both the upper and lower quench chambers was 30% and 25%respectively. Both the extrusion and calendaring process conditions arepresented in Table 19. The confirmation of good compaction at highspeeds is given in Table 20. And tensile properties of the webs aregiven in Table 21. The tensile properties were obtained using the WSP110.4 (05) EDANA ERT 20.2.89 (Option B) test method.

TABLE 19 extrusion and Calender Process conditions Calender CalenderCalender Temperature Throughput Pressure Temperature Pressure Run #Resin Composition (° C.) (kg/hr) (Pa) (° C.) (daN/cm) 1 93.5% A + 3% D +220 217 7500 145 60 3% E + 0.5% F 2 93.5% A + 3% D + 220 217 7500 145 603% E + 0.5% F 3 83.5% A + 10% 220 217 7500 145 60 B + 3% D + 3% E + 0.5%F 4 83.5% A + 10% 220 217 7500 145 60 B + 3% D + 3% E + 0.5% F 5 77.5%A + 19% 220 217 7500 130 60 B + 3% D + 0.5% F 6 88.5% A + 5% C + 220 2177500 146 60 3% D + 3% E + 0.5% F 7 88.5% A + 5% C + 220 217 7500 146 603% D + 3% E + 0.5% F Note: A = PLA 6202, B = PLA 6751, C = PLA 6302, D =PP, E = PEG/DOSS, F = Pigment

TABLE 20 Compaction at High Line Speeds Compac- Draft of Basis Line tionRoll the Cal- Run Weight Speed Tempera- ender # Resin Composition (gsm)(m/min) ture (° C.) (%) 1 93.5% A + 3% D + 3% 15 210 95 2.5 E + 0.5% F 293.5% A + 3% D + 3% 13.5 240 97 2.5 E + 0.5% F 3 83.5% A + 10% B + 15210 86 1 3% D + 3% E + 0.5% F 4 83.5% A + 10% B + 13.5 240 91 1.5 3% D +3% E + 0.5% F 5 77.5% A + 19% B + 14 225 95 0.5 3% D + 0.5% F 6 88.5%A + 5% C + 3% 15 210 95 1 D + 3% E + 0.5% F 7 88.5% A + 5% C + 3% 13.5240 104 1.2 D + 3% E + 0.5% FThe draft of the calender is the speed differential between the spinbeltand the calender. Low numbers is an indication of stable webs aftercompaction.

TABLE 21 Tensile properties of the webs Basis Normalized Normalized MDCD Weight MD Tensile CD Tensile MD Tensile CD Tensile ElongationElongation Run # Resin Composition (gsm) (N/5 cm) (N/5 cm) (mN * sqM/g)(mN * sqM/g) (%) (%) 1 93.5% A + 3% D + 3% E + 15 31.7 8.3 2113.3 553.314.3 13.8 0.5% F 2 93.5% A + 3% D + 3% E + 13.5 25.2 6.7 1866.7 496.311.4 23.2 0.5% F 3 83.5% A + 10% B + 3% D + 15 34.2 9.3 2280.0 620.014.4 25.8 3% E, 0.5% F 4 83.5% A + 10% B + 3% D + 13.5 27.8 7 2059.3518.5 13 26.1 3% E + 0.5% F 5 77.5% A + 19% B + 3% D + 14 34.2 9.32442.9 664.3 14.4 25.8 0.5% F 6 88.5% A + 5% C + 3% D + 15 31.2 9.42080.0 626.7 11.8 27 3% E + 0.5% F 7 88.5% A + 5% C + 3% D + 13.5 24.47.4 1807.4 548.1 13 24.8 3% E + 0.5% F

While the specification has described in detail certain exemplaryembodiments, it will be appreciated that those skilled in the art, uponattaining an understanding of the foregoing, may readily conceive ofalterations to, variations of, and equivalents to these embodiments.Accordingly, it should be understood that this disclosure is not to beunduly limited to the illustrative embodiments set forth hereinabove.Furthermore, all publications, published patent applications and issuedpatents referenced herein are incorporated by reference in theirentirety to the same extent as if each individual publication or patentwas specifically and individually indicated to be incorporated byreference. Various exemplary embodiments and details have been discussedabove for purposes of illustrating the invention, various modificationsmay be made in this invention without departing from its true scope,which is indicated by the following claims.

The invention claimed is:
 1. A method of making a web comprising:forming a mixture comprising: one or more thermoplastic polyestersselected from aliphatic polyesters and aromatic polyesters,polypropylene in an amount greater than 0% and no more than 10% byweight of the mixture; and a viscosity modifier selected from the groupconsisting of alkyl carboxylates, alkenyl carboxylates, aralkylcarboxylates, alkylethoxylated carboxylates, aralkylethoxylatedcarboxylates, alkyl lactylates, alkenyl lactylates, and mixtures thereofsimulataneously forming a plurality of fibers from the mixture; andcollecting at least a portion of the fibers to form a web, wherein theweb has at least one dimension which decreases by no greater than 10% inthe plane of the web when the web is heated to a temperature above aglass transition temperature of the fibers but below the meltingtemperature when measured in an unrestrained condition.
 2. The method ofclaim 1, wherein the web is formed using a melt-blowing, spun-bonding,or melt-spinning process.
 3. The method of claim 1, wherein thethermoplastic polyester and the viscosity modifier are mixed prior tothe web forming process.
 4. The method of claim 1, further comprisingthe step of extruding the polyester blended with the viscosity modifier.5. The method of claim 1, wherein the mixing of the polyester and theviscosity modifier comprises extruding the polyester and the viscositymodifier.
 6. The method of claim 1, further comprising post heating theweb.
 7. The method of claim 1, wherein the web is formed usingmelt-spinning, filament extrusion, electrospinning, gas jet fibrillationor combinations thereof.
 8. The method of claim 1, wherein the fibers donot exhibit molecular orientation.
 9. The method of claim 1, wherein themixture is a melt-processable mixture.
 10. The method of claim 1,wherein the web is in the form of a surgical drape, surgical gown,sterilization wrap, or wound contact material.